The Stanford University Heart Transplant Study (1974) was conducted to determine whether an experimental heart transplant program increased lifespan. Each patient entering the program was designated an official heart transplant candidate, meaning that he was gravely ill and would most likely benefit from a new heart. Some patients got a transplant and some did not. Of the 34 patients in the control group, 4 were alive at the end of the study. Of the 69 patients in the treatment group, 24 were alive. The contingency table below summarizes these results. Treatment Control Total Alive 24 4 28 Dead 45 30 75 Total 69 34 103 45 a) What proportion of patients in the treatment group died? 69 30 b) What proportion of patients in the control group died? 34 c) What are the claims being tested? Ho: The experimental heart transplant program does not increase HA: The experimental heart transplant program increases lifespan. lifespan. d) One approach for investigating whether or not the treatment is effective is to use a randomization technique. The steps below describes the set up for such approach, if we were to do it without using statistical software. Fill in the blanks with a number or phrase, whichever is appropriate. • First, we write alive on 28 V cards representing patients who were alive at the end of the study, and dead on 75 V cards representing patients who were not. • Second, we shuffle these cards and split them into two groups: one group of size representing treatment, and another group of size representing control. • Third, we calculate the difference between the proportion of dead cards in the treatment and control groups (Treatment - Control) and record this value. We repeat many times to build a distribution centered at the null value = • Fourth, we calculate the fraction of simulations where the simulated differences in proportions are less than the point estimate = the difference in proportions from the original sample (the difference in proportions from parts (a) and (b)). If this fraction is low, we conclude that it is unlikely to have observed such an outcome by chance and that the null hypothesis should be rejected in favor of the alternative. e) What is the estimated p-value, based on the 99 simulation results below? (Locate the point estimate and find the proportion of simulations equal to the point estimate or away from the null value.) f) What do the simulation results suggest about the effectiveness of the transplant program? O The p-value is large, so differences between treatment and control were likely just random chance. There is no evidence that the experimental heart transplant program increased the average patient's lifespan. O The p-value is small, so the differences between treatment and control were not likely from random chance alone. It appears the experimental heart transplant program increased the average patient's lifespan. -0.25 -0.15 -0.05 0.05 0.15 0.25 Simulated differences in proportions

In a 2009 study, a team of researchers recruited 38 men and divided them randomly into two groups - treatment or control. The also recruited 38 women and they randomly placed half the participants into the treatment group and the other half into the control group. One group was given 25 grams of chia seeds twice a day, and the other was given a placebo. The subjects volunteered to be a part of the study. After 12 weeks, the scientists found no significant difference between the groups in appetite or weight loss. Which of the following is true. (i) This is an observational study (ii) Blinding is used in this study because subjects in the control group recieved a placebo, so that htey were blinded to the treatment they recieved.  (iii) We can safely generalize the conclusion (that chia seeds have no significant effect on appetite or weight loss) from the participants to the population at large because randomization is used when assigning participatns to groups.

A recent study investigated whether cell phone users experience separation anxiety when they cannot access their phones. Because blood pressure increases with anxiety, the researchers used systolic blood pressure as an operational measure of anxiety. The experiment involved a random sample of cell phone users that were divided into two groups at random. One group of participants completed a survey while their phones were locked in a cabinet in a separate room and the other group of participants completed the same survey while their phones were nearby. (The survey questions were unrelated to cell phone use.) At the end of the survey, theresearchers measured each participant's systolic blood pressure. The same experiment was conducted in Montreal, Toronto, Vancouver, and St. Zotique. The blood pressure data needed is below. Use these data to answer the following question: compute r2 for the data collected in st. zotique. Please answer to 5 decimal places. Cell Phone (CP) No Cell Phone…

The following is based on information from The Wolf in the Southwest: The Making of an Endangered Species, by David E. Brown (University of Arizona Press). Before 1918, the proportion of female wolves in the general population of all southwestern wolves was about 50%. However, after 1918, southwestern cattle ranchers began a widespread effort to destroy wolves. In a recent sample of 37 wolves, there were only 11 females. One theory is that male wolves tend to return sooner than females to their old territories, where their predecessors were exterminated. Do these data indicate that the population proportion of female wolves is now less than 50% in the region? Use α = 0.01. (a) What is the level of significance? State the null and alternate hypotheses. O Ho: P 0.5 O Ho: P = 0.5; H₁: p 5 and nq > 5. O The Student's t, since np > 5 and ng > 5. The standard normal, since np < 5 and nq < 5. O The Student's t, since np < 5 and nq < 5. What is the value of the sample test statistic? (Round…

A study was performed to test the effectiveness of a new treatment for migraines. There were 125 patients in the study. Of these, 60 were randomly assigned to receive the standard treatment and 65 to receive the new treatment. All were instructed to take the medication at the onset of their next migraine and to notice if the pain of their migraine felt reduced after half an hour. Fifty patients receiving the new treatment reported reduced pain, compared with only 40 of the patients receiving the standard treatment. The results seem to favor the new treatment, but could the difference just be due to chance? In this problem, consider the null hypothesis that the percentage of patients with a reduction in pain is the same between the two treatments, versus the alternative hypothesis that the percentages are different. (a) Under the null hypothesis, the difference in the sample percentages is expected to be ___%. The standard error for the difference is estimated to be ___%. (b) Calculate…

A pharmaceutical company is testing the effectiveness of its vaccine across two different age brackets. They take a sample and split the participants up into two separate groups. Group A consists of 44 people who are between ages 13 and 18. Group B consists of 58 people between ages 19 and 26. After being administered the vaccine, it was found that 37 people from group A were immune to the virus and 42 people from group B were immune. (this is the same situation from the previous daily) Why do we use the 'pooled proportion' instead of the null hypothesis in the denominator of the test statistic? At a 10% significance level, is there reason to believe there is a difference in vaccine efficacy between Group A and Group B?  explain each step

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 55 people in the first group and this group will be administered the new drug. There are 45 people in the second group and this group will be administered a placebo. After one year, 11% of the first group has a second episode and 9% of the second group has a second episode. Conduct a hypothesis test to determine, at the significance level 0.1, whether there is reason to believe that the true percentage of those in the first group who suffer a second episode is different from the true percentage of those in the second group who suffer a second episode? Select the [Alternative Hypothesis,…

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 psychologist would like to examine the effects of a new drug on the activity level of animals. Three samples of rats are selected with n=5 in each sample. One group gets no drug, one group gets s small dose, and the third group gets a large dose. The psychologist records the activity level for each animal. The data from this experiment are presented below.   No drug Small dose Large dose 5, 3 , 1 , 1 , 5 5, 5, 9, 6, 5 10, 12, 9, 6, 8 =3, SS=16 =6, SS=12 =9, SS=20   Do these data indicate any significant differences among the three groups? Test with α=0.05.                        Compute the effect size and interpret the result.

At LLD Records, some of the market research of college students is done during promotions on college campuses, while other market research of college students is done through anonymous mail, phone, internet, and record store questionnaires. In all cases, for each new CD the company solicits an "intent-to- purchase" score from the student, with 0 being the lowest score ("no intent to purchase") and 100 being the highest score ("full intent to purchase"). The manager finds the following information for 105 intent-to-purchase scores for a soon-to-be-released CD: Sample Sample Sample size Group mean variance On campus 21 66.2 159.5 By mail 21 55.5 177.7 By phone 21 65.0 62.5 By internet 21 67.0 130.7 In a store 21 63.9 161.2 Send data to calculator Send data to Excel The manager's next step is to conduct a one-way, independent-samples ANOVA test to decide if there is a difference in the mean intent-to-purchase score for this CD depending on the method of collecting the scores. Answer the…