The midterm exam is open-book, but you are expected to observe the UTSPH Honor Code. Please be sure that your name is on each page of your exam answers. Integrate your computer output into your exam answers. Please submit a hard copy of your exam on the exam due date.

1. The Western Collaborative Group Study was a prospective study of 3154 healthy men, aged 35-60 years in 1960-61, who were employed in ten participating companies in California. Clinical coronary heart disease (CHD) was diagnosed in 257 men during a follow-up period of approximately nine years. The table below gives the incidence of CHD by five-year baseline age groups.

   	AGE GROUP
   CHD	35-40	41-45	46-50	51-55	56-60	Total
   Yes	31	55	70	65	36	257
   No	512	1036	680	463	206	2897
   Total	543	1091	750	528	242	3154

   
   Do these data demonstrate a significant linear age trend in CHD incidence? Using ptrend, analyze the data and write a summary of your findings that includes a graphical display of the observed CHD trend by age group.
2. A 2004 study published in the BMJ attracted quite a bit of worldwide media interest. The objective of the study was to determine whether dogs can be trained to identify people with bladder cancer on the basis of urine odor more successfully than would be expected by chance alone. Six dogs of varying breeds and ages completed a seven month period of training. The training objective was to enable the dogs to discriminate between urine from patients with bladder cancer and urine from control patients without bladder cancer. The dogs were taught to indicate which among several urine samples was from a bladder cancer patient by lying beside the sample.
   In the experiment each of six dogs was tested in nine trials. In each trial, one urine sample from a bladder cancer patient was randomly placed among six control samples. In the total of 54 trials with the six dogs, the dogs made the correct selection 22 times. Does this study support the conclusion that dogs can be trained to distinguish patients with bladder cancer on the basis of urine odor more successfully than would be expected by chance alone?
   2(a) State the null hypothesis and the alternative hypothesis.
   2(b) What statistical test procedure can be used to test the null hypothesis? Specify the test statistic and its distribution under the null hypothesis.
   2(c) Implement the test and report your findings.
3. Psychologists performed an experiment on male bank supervisors attending a management training course to investigate sex role stereotypes and personnel decisions. Among other tasks in their training course 48 supervisors were asked to make a decision on whether to promote a hypothetical applicant based on a personnel file. For half of them, the personnel file described a female applicant; for others the personnel file described a male applicant. The files were otherwise identical in all other respects. Results of the promotion decisions are given in the table below.

   	Promote	Do Not Promote	Total
   Male	21	3	24
   Female	14	10	24
   Total	35	13	48

   
   Based on the observed data, is there evidence of a bias against promotion of female applicants?
   3(a) State the null and alternative hypothesis.
   3(b) What statistical test procedure can be used to test the null hypothesis?
   3(c) Implement the test procedure and report your findings.
4. A 1986 clinical trial evaluated the effect of captopril on kidney function in insulin-dependent diabetic patients with nephropathy. Based on an analysis of systolic blood pressures of 16 randomized patients measured before and after one week’s treatment with captopril (n = 9) or placebo (n = 7), the authors concluded that "captopril represents a valuable new drug for treating hypertension in diabetics dependent on insulin with nephropathy". This conclusion was based on paired t-tests computed on the data in each group. The authors reported that captopril (for nine patients) significantly reduced systolic blood pressure (p-value < 0.05) whereas "no significant changes in occurred in seven patients treated with placebo".

Fortunately, the authors reported the original data in their research paper so readers could examine the statistical analysis that led the authors to their inference about the effect of captopril on systolic blood pressure. The data are provided in the attached Stata data file, captopril.dta and the file is described below.

. desc

Contains data from E:\captopril.dta

obs: 16 vars: 4 size: 160 (99.9% of memory free)

-----------------------------------------------------------------------------

storage display value

variable name type format label variable label

-------------------------------------------------------------------------------

id byte %8.0g patient id

baseline int %8.0g baseline SBP (mm Hg)

wk1 int %8.0g SBP after 1 week

cpril byte %8.0g captopril = 1 placebo = 0

-----------------------------------------------------------------------------

(1a) Using this data file reproduce the results on systolic blood pressure given in Table IV of the research paper.

(1b) What is wrong with their analysis, and their interpretation of the results?

(1c) Perform a correct analysis. Use graphical and statistical methods to analyze the systolic blood pressure data.

(1d) What conclusions can be drawn about the effect of captopril on systolic blood pressure? Write a summary of your statistical findings and conclusions.

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Solution: The downloadable solution consists of 11 pages, 1348 words and 13 charts.
Deliverable: Word Document