2. In a large clinic located in an inner city hospital, 56 patients with non-symptomatic HIV infection have been treated with an experimental drug believedto have the capability of restoring certain immune system functions associatedwith HIV infection. Of these patients, 12 had CD4 cell counts below 250 at theinitial visit, 20 had counts between 250 and 400, and 24 had counts above 400.(The lower the count, the worse the prognosis.) It is desired to take a stratifiedrandom sample of 30 patients, 10 from each of the three groups describedabove, for purposes of estimating the 12-month incidence of AIDS-definingevents among these patients. The results of this sample survey are shownbelow:Number of PersonsCD4 Level250-399220a. How many samples of 30 patients taken as described above are possible?b. Estimate the proportion of patients having one or more AIDS-definingevents.c. What is the estimated standard error of this estimated proportion?d. A simple random sample (without stratification) of 30 of these patientsyielded the following data:Number of Events0123Number of Events01232< 2506722N511< 2503102Number of PersonsCD4 Level250-3998210400 and Over91O400 and Over12010i. How many samples of size 30 are possible under simple randomsampling without stratification?ii. Estimate the incidence of AIDS-defining events from these dataand the estimated standard error of this estimated proportion.iii. Compare this with the results obtained from the stratified samplingdesign. Which design produces the more reliable estimate? Whydoes it?

Given:- In a large clinic located in an inner city hospital, 56 patients with non-…

Answered: 2. In a large clinic located in an…

MATLAB: An Introduction with Applications

6th Edition

ISBN:9781119256830

Author:Amos Gilat

Publisher:Amos Gilat

Chapter1: Starting With Matlab

Section: Chapter Questions

Problem 1P

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A study was conducted to determine whether big-city and small-town dwellers differed in their helpfulness to strangers. In this study, the investigators rang the doorbells of strangers living in a large City or small towns in the vicinity. They explained they had misplaced the address of a friend living in the neighbourhood and asked to use the phone. The following data show the number of individuals who admitted or did not admit the strangers (the investigators) into their homes: Helpfulness to strangers Admitted strangers into their home Didnot admit strangers into their home Big city dwellers 60 90 Small town dwellers 70 30 State the dependent and independent variable Is this a directional or non directional
A study published in JAMA in 2004 examined past results of other studies on bariatric surgery. Bariatric surgery is done to replace the size of the stomach in various ways. It is typically used on only obese patients, and one the traditional form of the surgery, gastric bypass has a 1% mortality (death) rate caused by surgery. However, in the studies reporting on the effects of the surgery on Type ll diabetes, 1417 of 1846 diabetic patients recovered completely from diabetes after surgery. These patients no longer need medication like insulin (which is injected into the skin) or pills to help manage blood sugar. In a study released a decade later, the percentage of patients who recover from diabetes has increased 80%. Using confidence intervals determine whether this is a significant change from the 2004 data. Use n=2000
It has been observed that some persons who suffer colitis, again suffer colitis within one year of the first episode. This is due, in part, to damage from the first episode. The performance of a new drug designed to prevent a second episode is to be tested for its effectiveness in preventing a second episode. In order to do this two groups of people suffering a first episode are selected. There are 170 people in the first group and this group will be administered the new drug. There are 132 people in the second group and this group wil be administered a placebo. After one year, 14% of the first group has a second episode and 18% of the second group has a second episode. What is a 90% confidence interval for the difference in true proportion of the two groups/
In an article published in 2012 at Telegraph.co.uk, Warranty Direct gave engine failure rates for a variety of car brands based on their database of UK direct consumer warranties. The following are known: ● Hondas failed at a rate of 1 in 344. ● Fords failed at a rate of 1 in 80. ● Audis failed at a rate of 1 in 27. Suppose Hondas account for 20% of sales at a particular dealer, Audis 30%, and Fords 50%. Assuming the engine failure rates apply to these vehicles. Determine the probability that a randomly selected vehicle from this dealer will experience engine failure.
A study published in JAMA in 2004 examined past results of other studies on bariatric surgery. Bariatric surgery is done to replace the size of the stomach in various ways. It is typically used on only obese patients, and one the traditional form of the surgery, gastric bypass has a 1% mortality (death) rate caused by surgery. However, in the studies reporting on the effects of the surgery on Type ll diabetes, 1417 of 1846 diabetic patients recovered completely from diabetes after surgery. These patients no longer need medication like insulin (which is injected into the skin) or pills to help manage blood sugar. If you had a morbidly obese relative with diabetes what would you tell him or her about bariatric surgery? Explain. Would you recovered it? Why/ why not?
Imagine you work for a large company that sells a variety of cleaning supplies deigned to prevent the spread of viruses. You decide to investigate what the best method for preventing the spread of viruses is, if only one method is used. You design experiments with the following groups: hand sanitizer only, hand washing without soap, hand washing with soap, along with a control group. Each group has 181 observations during testing, beginning with a certain amount of the viruses present before treatment is applied. The amount of germs is being measured. You find a sum of squares between treatments of 578.59, along with a sum of squares error of 5022.05. Using this information, what is the F-statistic of your analysis?

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