课程名称︰统计导论 课程性质︰数学系选修 课程教师︰江金仓 开课学院：理学院 开课系所︰数学系 考试日期（年月日）︰2016.11.2 考试时限（分钟）：50 试题 : Introduction to Statistics (Test 2) 1.(30%) State or explain the following terms. (1a) stratified random sampling. (1b) case-control study. (1c) retrospective study. (1d) confounding variable. (1e) Hawthorne effect. (1f) five number summary. 2.(10%) Draw a box-plot via using the five number summary: minimum=63, maximum=72, the first quartile=68, median=70, the third quartile=71. 3. Let X be the scores of an entrance examination with mean 60 and standard deviation 5. (3a)(5%) Define the corresponding Z-score of X variable. (3b)(5%) What is the original score of Z=2? 4.(10%) Compute the coefficient of variation of the grouped data with f_1,f_2, ...,f_g being the frequencies of the g classes [a_0,a_1), [a_1,a_2),..., [a_(g-1),a_g]. 5.(10%) A case control study in Berlin asked 239 lung cancer patients and 429 controls (matched to the cases by age and sex) whether they kept a pet bird during adulthood. Of the 239 lung cancer cases, 98 said yes. Of the 429 controls, 101 said yes. Construct a contingency table for the data. 6. Let r_XY be the correlation coefficient of the sample {(X_1,Y_1),..., (X_n,Y_n)}. (6a)(7%) Compute the sample correlation coefficient r_XY of X and Y variables. (6b)(2%)(2%)(2%) Explain the meanings of r_XY=1, r_XY=-1, and r_XY=0, respectively. (6c)(7%) For the re-scaled data {(U_1,V_1),...,(U_n,V_n)} with U_i=a(X_i)+b and V_i=c(Y_i)+d, where a and c are positive constants and b and d are any constants, let r_UV stand for the sample correlation coefficient of U and V Variables. Find the relation between r_UV and r_XY. (6d)(10%) Compout r_XY for Y_i=β_0+β_1(X_i), i=1,...,n, where β_1>0. --

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