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L. Mojok. South Texas College of Law.

The radial artery approach buy discount kamagra oral jelly erectile dysfunction in diabetes mellitus pdf, while safer purchase kamagra oral jelly 100 mg erectile dysfunction 43, may be impractical because use of the large size of catheters used for ablation purchase kamagra oral jelly 100mg fast delivery erectile dysfunction medicine in ayurveda. The transseptal approach can be used in such cases, although, in my experience with current catheter technology, accessing the entire ventricle is more difficult than by the retrograde approach. The use of noncontact mapping catheters may require a transseptal approach for their placement. A transseptal puncture is necessary to place the ablation catheter if the retrograde approach is not feasible. In all instances, we use full heparinization with 5,000 to 10,000 U as a bolus and 1,200 to 3,000 U/h drip, adjusted to maintain an activated clotting time of 250 to 350 seconds. During the spontaneous or induced tachycardia, we record bipolar and unipolar electrograms (poles 1 and 2) as the catheter is positioned at each new mapping site. In patients with large scars unfiltered unipolar signals are dominated by cavity potentials making it difficult/impossible to see small, local activity. If possible we record at variable and fixed (l cm = 1 mV) gains to be able to standardize duration measurements. Normal values for voltage need to be ascertained for each electrode catheter because electrogram amplitude and duration are affected by electrode size (the tip is the largest) and interelectrode distance, as well as the relation of the distal and proximal poles to the site of contact and wavefront of activation (see discussion below). This is very important if one tries to compare substrate voltage using very small electrodes and small interelectrode distance (Rhythmia and PentArray catheters). If catheters have a 2-5-2 or greater interelectrode distance, we obtain distal and proximal bipolar electrograms by recording from the tip and the third electrode (distal pair) of the quadripolar catheter and use the second and fourth poles to record electrical activity adjacent to or overlapping the site of origin (proximal pair) when we use stimulation from the distal and third poles. Thus, recording and stimulation occur over a shared area, which electrophysiologically is “large” in terms of source of recorded signal. If we use a catheter with a 2- mm interelectrode distance, poles 1 and 2 are used as the distal pair and 3 and 4 as the proximal pair. Recording from multiple bipolar pairs from a multipolar electrode catheter in the left ventricle (particularly if bipolar pairs are >1 cm apart) is inappropriate, because one has no control over the degree of contact of the proximal electrode pairs and/or their distance from the ventricular wall. The only accurate data are from electrograms recorded from electrodes in contact with the endocardium. One should therefore use only electrograms recorded from a bipolar pair that includes the tip electrode, because it is almost always in contact with the endocardium. A proximal electrode pair is useful for analyzing events during pacing since polarization of the distal electrodes makes simultaneous recording and pacing not possible in most available laboratory systems. Contact is critical when a standard quadripolar, decapolar, or basket catheters are used. The degree of contact can be assessed by pacing thresholds or impedance measurements at each electrode pair. This “chamber” is limited by the absence of direct confirmation of contact of the roving catheter. Newer technology is being incorporated into this system, which has improved and will continue to improve its anatomic localizing capability. However as noted above, the activation times are interpolated on the basis of the inverse solution for 64 poles. The advantages of unipolar electrograms are that they provide a more precise measure of local activation, because the maximum negative dV/dt corresponds to the maximum Na+ conductance. The disadvantages of unipolar recordings are that they have a poor signal-to-noise ratio and distant activity can be difficult to separate from local activity. On the other hand, bipolar recording techniques provide an improved signal-to-noise ratio and reduce the effect of distant activity on the local electrogram (Fig. While local activation is less precisely defined, the peak amplitude of a filtered (30 to 500 Hz) close (2 to 5mm) bipolar recording of a “normal” electrogram corresponds to the maximum negative dV/dt of the unipolar recording. Variable low- and/or high-pass filters can give different amplitudes, duration, shape, etc. Although a bipolar electrode pair, positioned perpendicular to the direction of propagation of the wavefront, should theoretically result in the absence of an electrical signal, this is rarely a problem. Nevertheless, the electrogram amplitude may be diminished when propagation is relatively perpendicular to the recording electrodes. Use of very small electrodes and interelectrode distance (1 mm) overcomes many of the limitations that standard mapping/ablation catheters have because their tip is 3. One therefore cannot obtain directional information from an isolated bipolar electrogram recorded from a standard mapping/ablation catheter. Defining the site of origin (or exit from a protected isthmus in a reentrant circuit) and the overall pattern of activation of impulse propagation requires detailed recordings from multiple sites. Filtered or unfiltered unipolar recordings are valuable in determining the relative contributions of the distal and second pole of the bipolar pair. Clear demonstration that the distal pole is earliest is necessary to assure the highest success of ablation (see Chapter 13). As stated in earlier paragraphs, several factors affect electrogram amplitude and width, including (a) conduction velocity (the greater the velocity the higher the peak amplitude of the unfiltered and filtered bipolar electrogram); (b) the mass of activated tissue; (c) the distance between the electrodes and the propagating wavefront; (d) the direction of the propagation relative to the bipoles (Figs. The fact that most catheters used for mapping have a 4-mm ablation tip results in inherent limitations of accuracy, even for 2 unipolar recordings. This takes away some of the theoretical advantages of unipolar over bipolar recordings. The very small electrodes and small interelectrode distance of the Rhythmia basket have recorded discrete potentials in areas of <0. The larger tip records from a larger area that can lead to cancellation effects on the recorded signal. Unipolar and derived 2 bipolar recordings are shown from electrodes G1, G2, and H2 which are each 0. The unipolar signals show G1 and G2 are activated nearly simultaneously producing a bipolar signal of 0. When the bipolar signal is recorded between G2 and H2, there is a slight difference in local activation and the recorded electrogram has a normal voltage of 1. Peak-to-peak bipolar voltage is shown on the ordinate and activation time between the two unipolar signals from which the bipolar electrogram is derived. When the poles are perpendicular to the surface, the difference between the unipolar activation is close to 0 and the bipolar voltage is low. When the electrodes are parallel to the surface the bipolar amplitude depends on the activation times between the electrodes. Using 1-mm electrodes, the peak bipolar voltage is recorded with 6 mm, but gradually decreases at wider interelectrode distances. Acquisition and Interpretation of Activation Mapping During Ventricular Tachycardia The “site of origin” of a tachycardia is determined by locating the earliest recorded discrete or fractionated ventricular electrogram closest to mid-diastole. In this section the discussion will be based on recordings from standard ablation catheters. Thus, while the earliest presystolic electrogram closest to mid-diastole is the most commonly used definition for the “site of origin,” continuous diastolic activity and/or bridging of diastole at adjacent sites or mapping a discrete diastolic pathway would be most compatible with recording from a reentrant circuit. As shown in Figure 11-213 complete reentrant circuits may be able to be recorded as the Rhythmia system or the PentArray and Carto system.

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The nine positions correspond to testing knee flexion angles of 1–10 order kamagra oral jelly overnight erectile dysfunction hypothyroidism, 11–20 buy generic kamagra oral jelly 100 mg line best erectile dysfunction vacuum pump, 21–30 buy kamagra oral jelly 100 mg otc impotence 22 year old, 31–40 , 41–50 ,51–60, 61–70 ,71–80, and 81–90. May weconclude, onthe basisof these data, that mean severity scoresdifferamongthethreepopulationsrepresentedinthestudy? Use Tukey’s procedure to test for significant differences among individual pairs of sample means. No dural ectasia: 18, 18, 20, 21, 23, 23, 24, 26, 26, 27, 28, 29, 29, 29, 30, 30, 30, 30, 32, 34, 34, 38 Mild dural ectasia: 10, 16, 22, 22, 23, 26, 28, 28, 28, 29, 29, 30, 31, 32, 32, 33, 33, 38, 39, 40, 47 Marked dural ectasia: 17, 24, 26, 27, 29, 30, 30, 33, 34, 35, 35, 36, 39 Source: Data provided courtesy of Reed E. The following table shows the arterial plasma epinephrine concentrations (nanograms per milliliter) found in 10 laboratory animals during three types of anesthesia: Animal Anesthesia 1 2 3 4 5 6 7 8 9 10 A. She studied 35 patients with a stroke lesion in the right hemisphere and 19 patients with a lesion on the left hemisphere. She also grouped lesion size as 2 ¼ “1-3 cm”; 3 ¼ “3-5 cm”; and 4 ¼ “5 cm or greater” One of the outcome variables was a measure of each patient’s total unawareness of their own limitations. Unawareness Score Lesion Size Left Right Group Hemisphere Hemisphere 2 13 11 10 10 13 9 11 10 9 9 10 10 9 8 10 8 3 8 10 10 12 10 14 11 10 8 4 13 13 9 14 10 19 13 10 10 14 15 9 Source: Data provided courtesy of 8 Adina Hartman-Maeir, Ph. A random sample of the records of single births was selected from each of four populations. The following table shows the aggression scores of 30 laboratory animals reared under three different conditions. One animal from each of 10 litters was randomly assigned to each of the three rearing conditions. Rearing Condition Extremely Moderately Not Litter Crowded Crowded Crowded 1 2 3 4 5 6 7 8 9 10 30 20 20 Do these data provide sufficient evidence to indicate that level of crowding has an effect on aggression? The following table shows the vital capacity measurements of 60 adult males classified by occupation and age group: Occupation Age Group A B C D 1 4. If an overall significant difference is found, determine which pairs of individual sample means are significantly different. In addition to studying the 12 type 2 diabetes subjects (group 1), Polyzogopoulou et al. The following data are the 12-month post- surgery fasting glucose levels for the three groups. For exercises 34 to 38 do the following: (a) Indicate which technique studied in this chapter (the completely randomized design, the randomized block design, the repeated measures design, or the factorial experiment) is appropriate. Johnston and Bowling (A-37) studied the ascorbic acid content (vitamin C) in several orange juice products. One of the products examined was ready-to-drink juice packaged in a re-sealable, screw- top container. One analysis analyzed the juice for reduced and oxidized vitamin C content at time of purchase and reanalyzed three times weekly for 4 to 5 weeks. Enrolled in the study were 18 women with pre-eclampsia, 18 normal pregnant women, and 18 nonpregnant female matched controls. They performed a factorial experiment with two donor cell types (Sertoli cells or cumulus) and six genotypes. Outcome variables were the cleavage rate and the birth rate of pups in each treatment combination. Subjects were children ages 6 months to 12 years undergoing living-related liver transplantation due to congenital biliary atresia and severe liver cirrhosis. Among the data collected were the following serum total bilirubin (mg/dl) levels after transplantation (h–hours, d–days): Time After Reperfusion of Donor Liver Preoperative Liver Transection Anhepatic Phase 1 h 2 h 4 h 8 h 1 d 2 d 3 d 6. The purpose of a study by Sakakibara and Hayano (A-43) was to examine the effect of voluntarily slowed respiration on the cardiac parasympathetic response to a threat (the anticipation of an electric shock). Subjects were 30 healthy college students whose mean age was 23 years with a standard deviation of 1. An equal number of subjects were randomly assigned to slow (six males, four females), fast (seven males, three females), and nonpaced (five males, five females) breathing groups. Subjects in the slow- and fast-paced breathing groups regulated their breathing rate to 8 and 30 cpm, respectively. The following are the subjects’ scores on the State Anxiety Score of State-Trait Anxiety Inventory after baseline and period of threat: Slow paced Fast paced Nonpaced Baseline Threat Baseline Threat Baseline Threat 39 59 37 49 36 51 44 47 40 42 34 71 48 51 39 48 50 37 50 61 47 57 49 53 34 48 45 49 38 52 54 69 43 44 39 56 34 43 32 45 66 67 38 52 27 54 39 49 44 48 44 44 45 65 Source: Data provided courtesy 39 65 41 61 42 57 of Dr. Twenty-four adult cats were divided into four groups on the basis of a measure of spinal cord function plus a control group that did not undergo spinal compression. Among the data collected were the following compression ratio [(sagittal diameter/transverse diameter) Â100] values after 5 hours of compression: Control 80. Pentoxifylline was not administered to animals in group 1 (C), was administered only during the reperfusion period (P) to animals in group 2, and was administered only in the flush solution to animals in group 3 (F). The following are the aortic pressure readings for each animal during the 6-hour assessment period: 0 60 120 180 240 300 360 Group min min min min min min min à C 85. Each participant completed a 30-km cycling time trial under two conditions, following ingestion of sodium citrate and following ingestion of a placebo. The 90 subjects ranged in age from 13 to 52 years and were divided into the following four groups on the basis of clinical findings regarding the nature of instability of the knee: normal (no symptoms or signs related to the knee), lateral, medial, and multidirectional instability. Among the data collected were the following latencies (seconds) to the first pain response induced by radiant heat stimulation at three different skin temperatures: Subject 25 C 1 6. A study for the development and validation of a sensitive and specific method for quantifying total activin-A concentrations has been reported on by Knight et al. Twelve healthy men, ages 22 through 35 years, yielded the following serum T3ðnmol=LÞ levels at 0800 hours after 8 (day 1), 32 (day 2), and 56 (day 3) hours of fasting, respectively. Subjects were participants in a study of fasting-induced alterations in pulsatile glycoprotein secretion conducted by Samuels and Kramer (A-54). Subject T3 Day Subject T3 Day Subject T3 Day Subject T3 Day 1 88 1 2 115 1 3 119 1 4 164 1 1 1 Subject T3 Day Subject T3 Day Subject T3 Day Subject T3 Day 5 93 1 6 119 1 7 152 1 8 121 1 5 5 113 3 6 44 3 7 74 3 8 133 3 Subject T3 Day Subject T3 Day Subject T3 Day Subject T3 Day 9 108 1 10 124 1 11 102 1 12 131 1 9 93 2 10 97 2 11 56 2 12 83 2 9 75 3 10 74 3 11 58 3 12 66 3 Source: Data provided courtesy of Dr. To determine the nature and extent to which neurobehavioral changes occur in association with the toxicity resulting from exposure to excess dietary iron (Fe), Sobotka et al. The researchers randomly assigned the animals, according to ranked body weights, to one of five diet groups differentiated on the basis of amount of Fe present: Control—35 (1), 350 (2), 3500 (3), 4 (iron deficient) (4), and 20,000 (5) ppm, respectively. Hansen (A-56) notes that brain bilirubin concentrations are increased by hyperosmolality and hypercarbia, and that previous studies have not addressed the question of whether increased brain bilirubin under different conditions is due to effects on the entry into or clearance of bilirubin from brain. In a study, he hypothesized that the kinetics of increased brain bilirubin concentration would differ in respiratory acidosis (hypercarbia) and hyperosmolality. Forty-four young adult male Sprague-Dawley rats were sacrificed at various time periods following infusion with bilirubin. The following are the blood bilirubin levels mmol=L of 11 animals just prior to sacrifice 60 minutes after the start of bilirubin infusion: Controls Hypercarbia Hyperosmolality 30 48 102 94 20 118 78 58 74 52 74 Source: Data provided courtesy of Dr. Among the data collected were the following breathing frequency scores of subjects 18 months after rehabilitation: Group Group 1 12 16 24 12 16 24 16 14 16 12 12 14 16 12 18 14 12 15 14 12 18 16 12 16 12 18 24 12 12 16 12 12 24 12 15 18 12 10 18 20 16 Source: Data provided courtesy of Dr. Among the data collected were the following ages of three groups of caregivers of a demented relative living at home: husbands, wives, and adult daughters. Using subjects with severe mental retardation (mean age 16 years) who had been living in institutions for most of their lives, Takahashi et al.

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Proceedings of the 12th Meeting of the International Continence Society order kamagra oral jelly discount safe erectile dysfunction pills, Leiden cheapest kamagra oral jelly impotence forum, the Netherlands generic 100mg kamagra oral jelly visa crestor causes erectile dysfunction, 1982, p. A cost utility analysis of tension free vaginal tape versus colposuspension for primary urodynamic stress incontinence. Cost effectiveness analysis of open colposuspension versus laparoscopic colposuspension in the treatment of urodynamic stress incontinence. Updated systematic review and meta-analysis of the comparative data on colposuspensions, pubovaginal slings, and mid-urethral tapes in the surgical treatment of female stress urinary incontinence. The ideal material for the construction of a pubovaginal sling is sterile, biocompatible, noncarcinogenic, and consistent in quality. In the literature, several allograft, xenograft, and synthetic materials meeting these criteria have been studied. Allograft and xenograft materials are not commonly used for pubovaginal slings because of questions about their durability and cost. In addition, while synthetic meshes are certainly durable, they do carry the potential drawbacks of higher rates of graft infection, urinary tract perforation, and vaginal exposure. Outcomes data have shown that synthetic pubovaginal slings are 15 times more likely to perforate into the urethra (0. For these reasons and others, autologous fascial slings remain the material of choice. In 1990, Petros and Ulmsten proposed a unifying concept called the integral theory [3]. This theory stated that the most important factors for preserving continence were adequate function of the pubourethral ligaments, the suburethral vaginal hammock, and the pubococcygeus muscle. The authors postulated that injury to any of these three components from surgery, parturition, aging, or hormonal deprivation could lead to impaired midurethral function and subsequently urinary incontinence. Dynamic ultrasound studies have shown that stress maneuvers can cause the posterior wall of the urethra to slide away from the anterior urethral wall and allow for opening of the bladder neck and proximal urethra (funneling), resulting in the loss of urine [4]. While not all elements of vaginal prolapse require repair, consideration must be given to addressing prolapse at or distal to the hymenal ring, or symptomatic prolapse of a lesser degree. An in-office cough stress test should also be performed on all patients and confirming the diagnosis in this manner is helpful. Some clinicians may also find quantitative measurement of urethral hypermobility and a voiding diary helpful. A preoperative bowel preparation is not needed unless a concomitant hysterectomy, vaginal vault suspension, or posterior compartment surgery is planned. As with any surgical intervention, a thorough discussion of the risks, benefits, and alternative therapies needs to be undertaken. Intraoperative risks include bleeding (with potential for transfusion); injury to the bladder, urethra, or bowel; and hematoma formation. For autologous slings, harvest site complications include seroma formation, wound infection, and incisional hernia formation. As with all surgical procedures, preoperative discussion should also include mention of the rare but serious risks of cardiovascular, pulmonary, and thromboembolic events. In the authors’ opinion, sequential compression devices should be placed on the bilateral lower extremities prior to the induction of anesthesia. Prior to the start of the procedure, patients should receive a single dose of one of the following: a first- or second-generation cephalosporin, aztreonam (in cases of renal insufficiency), an aminoglycoside plus metronidazole, or clindamycin [7]. The patient is then positioned in a slightly exaggerated dorsal lithotomy position. The abdomen just above the umbilicus and the vagina are prepped with povidone-iodine or chlorhexidine gluconate solutions. After draping, a weighted speculum is placed in the vagina and an 18 F Foley catheter is inserted into the urethra and placed to continuous gravity drainage. Fascial Harvest A Pfannenstiel incision is made approximately 2 cm above the pubic symphysis, providing excellent exposure and cosmesis. In women with a history of prior pelvic surgery, a preexisting skin incision can also be used. The skin and Scarpa’s layer are left open for passage of sling sutures later in the procedure. The graft is then bluntly separated from the underlying muscle and transected as far distally as possible. Immediate compression should be applied to the thigh to constrict perforating vessels. A compressive wrap is then placed for 8 hours postoperatively and early ambulation is encouraged [8]. The rent in the rectus fascia is closed while the skin and Scarpa’s fascia are left open. Alternatively, a vertical midline incision can be made if concomitant anterior or apical compartment surgery is planned. The vaginal mucosa is then dissected sharply off the underlying surface of the pubocervical and periurethral fascia, with lateral dissection proceeding up to the inferior edge of the pubic symphysis. The scissors should be aimed at the ipsilateral shoulder and remain just inferior to the pubic symphysis. Once the endopelvic fascia is perforated, periurethral adhesions in the retropubic space are released manually with an index finger (Figure 72. With this dissection, the infrapubic and retropubic dissection planes are now connected. During this step, it is important to ensure that the retropubic space is fully opened. The posterior surface of the pubic symphysis should be easily palpable with very little intervening tissue. Sling Placement and Fixation If not already done, bladder drainage is again ensured. A finger in the retropubic space is then used to carefully guide Stamey needles from the abdominal incision into the vaginal incision on either side of the urethra (Figure 72. Cystoscopy with a 70° lens is then performed to diagnose inadvertent bladder perforation. Indigo carmine is given intravenously to document ureteral integrity via efflux of blue urine bilaterally. If bladder perforation is identified, the needle can be repositioned until it is outside the bladder and the surgery can proceed. The midportion of the sling is positioned over the bladder neck and the distal aspect is sutured to the periurethral tissue with two simple 4-0 polyglactin 910 sutures. Adjusting Sling Tension and Abdominal Wound Closure Sling tension is then set from the abdominal incision. Before tying a 3rd knot, a cystoscope sheath is passed into the bladder to ensure that there is no hitch. If significant resistance is encountered, the two knots can be undone and the tension adjusted until the sheath passes without a hitch. Once the sling is correctly tensioned, Scarpa’s fascia is reapproximated with an interrupted 3-0 absorbable suture.

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Since this interval does not include 0 discount kamagra oral jelly 100 mg with mastercard impotence female, we say that 0 is not a candidate for the difference between population means purchase 100 mg kamagra oral jelly overnight delivery erectile dysfunction age 29, and we conclude that the differenceisnotzero purchase kamagra oral jelly 100mg otc young healthy erectile dysfunction. Sampling from Normally Distributed Populations: Population Variances Unknown As we have learned, when the population variances are unknown, two possibilities exist. We consider first the case where it is known, or it is reasonable to assume, that they are equal. A test of the hypothesis that two population variances are equal is described in Section 7. Population Variances Equal When the population variances are unknown, but assumed to be equal, we recall from Chapter 6 that it is appropriate to pool the sample variances by means of the following formula: ð n À 1 s2 þ n À 1 s2 2 1 1 2 2 sp ¼ n1 þ n2 À 2 When each of two independent simple random samples has been drawn from a normally distributed population and the two populations have equal but unknown variances, the test statistic for testing H0: m1 ¼ m2 is given by ð x1 À x2 m1 À m2 0 t ¼ sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi (7. Subjects used a modified wheelchair to incorporate a rigid seat surface to facilitate the specified experimental measurements. Interface pressure measurement was recorded by using a high-resolution pressure-sensitive mat with a spatial resolution of four sensors per square centimeter taped on the rigid seat support. During static sitting conditions, average pressures were recorded under the ischial tuberosities (the bottom part of the pelvic bones). The data constitute two independent simple random samples of pressure measurements, one sample from a population of control subjects and the other sample from a population with lower-level spinal cord injury. We shall assume that the pressure measurements in both populations are approximately normally distributed. When the null hypothesis is true, the test statistic follows Student’s t distribution with n1 þ n2 À 2 degrees of freedom. Chow, “Pelvic Movement and Interface Pressure Distribution During Manual Wheelchair Propulsion,” Archives of Physical Medicine and Rehabilitation, 84 (2003), 1466–1472. We fail to reject H0, since À1:7341 < À:569; that is, À:569 falls in the nonrejection region. The critical value of t0 for a one-sided test is 1ÀðÞa=2 2 found by computing t0 by Equation 7. For a two-sided test, reject H if the computed value of t0 is either greater than or 0 equal to the critical value given by Equation 7. Fora one-sided testwiththerejectionregioninthe right tailofthesamplingdistribution, reject H if the computed t0 is equal to or greater than the critical t0. For a one-sided test with a 0 left-tail rejection region, reject H if the computed value of t0 is equal to or smaller than the 0 negative of the critical t0 computed by the indicated adaptation of Equation 7. Measures of this variable were calculated from the aortic diameter evaluated by M-mode echocardiography and blood pressure measured by a sphygmomanometer. In the 15 patients with hypertension (group 1), the mean aortic stiffness index was 19. We wish to determine if the two populations represented by these samples differ with respect to mean aortic stiffness index. The sample sizes, means, and sample standard deviations are: n1 ¼ 15; x1 ¼ 19:16; s1 ¼ 5:29 n2 ¼ 30; x2 ¼ 9:53; s2 ¼ 2:69 2. The data constitute two independent random samples, one from a population of subjects with hypertension and the other from a control population. We assume that aortic stiffness values are approxi- mately normally distributed in both populations. Before computing t0 we calculate w ¼ 1 2 2 ð 5:29 =15 ¼ 1:8656 and w2 ¼ 2:69 =30 ¼ :2412. On the basis of these results we conclude that the two population means are different. This will allow the use of normal theory since the distribution of the difference between sample means will be approximately normal. When each of two large independent simple random samples has been drawn from a population that is not normally distributed, the test statistic for testing H0: m1 ¼ m2 is ð x1 À x2 m1 À m2 0 z ¼ sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi (7. If the population variances are known, they are used; but if they are unknown, as is the usual case, the sample variances, which are necessarily based on large samples, are used as estimates. Sample variances are not pooled, since equality of population variances is not a necessary assumption when the z statistic is used. One focus of the study was to determine if there were differing levels of the anticardiolipin antibody IgG in subjects with and without thrombosis. McNearney, “Analysis of Risk Factors and Comorbid Diseases in the Development of Thrombosis in Patients with Anticardiolipin Antibodies,” Clinical Rheumatology, 22 (2003), 24–29. The statistics were computed from two independent samples that behave as simple random samples from a population of persons with thrombosis and a population of persons who do not have thrombosis. Since the population variances are unknown, we will use the sample variances in the calculation of the test statistic. Since we have large samples, the central limit theorem allows us to use Equation 7. When the null hypothesis is true, the test statistic is distributed approximately as the standard normal. These data indicate that on the average, persons with thrombosis and persons without thrombosis may not have differing IgG levels. When testing a hypothesis about the difference between two populations means, we may use Figure 6. Alternatives to z and t Sometimes neither the z statistic nor the t statistic is an appropriate test statistic for use with the available data. When such is the case, one may wish to use a nonparametric technique for testing a hypothesis about the difference between two population measures of central tendency. The Mann-Whitney test statistic and the median test, discussed in Chapter 13, are frequently used alternatives to the z and t statistics. For each exercise, as appropriate, explain why you chose a one-sided test or a two-sided test. Discuss how you think researchers or clinicians might use the results of your hypothesis test. What clinical or research decisions or actions do you think would be appropriate in light of the results of your test? The investigators recruited 31 postmenopausal women with ankle fractures and 31 healthy postmenopausal women to serve as controls. One of the variables of interest was the length from the most superoanterior point of the body of the hyoid bone to the Frankfort horizontal (measured in millimeters). Do these data provide sufficient evidence to allow us to conclude that the two sampled populations differ with respect to length from the hyoid bone to the Frankfort horizontal? Eighty-two subjects with essential hypertension were randomly assigned to an intervention or a control group. The intervention group received monthly monitoring by a research pharmacist to monitor blood pressure, assess adherence to treatment, prevent, detect, and resolve drug-related problems, and encourage nonpharmaco- logic measures for blood pressure control. The changes after 6 months in diastolic blood pressure (pre À post, mm Hg) are given in the following table for patients in each of the two groups.