第七章基于两个样本的推断：置信区间和假设检验.ppt

59 The sampling distribution is a function of the sample sizes upon which the sample variances are based. Hint: Recall the formula for variance! s2 = Σ(x -?x)2/(n-1) Key words that show a test on variances, not on means or proportions: variance, standard deviation, variability, variation, scatter, dispersion. F ratio is a statistic defined as the ratio of 2 independent estimates of a normally distributed population’s variance. Note: degrees of freedom refer to numerator and denominator 66 The lower F is not the reciprocal of the upper F. What do you do if equal sample sizes? 68 69 68 Allow students about 15 minutes to solve this. 72 73 72 As a result of this class, you will be able to ... 45 Just take the mean and standard deviation of the difference. SD is simply the standard deviation. Just take the mean and standard deviation of the difference. SD is simply the standard deviation. Why related populations? Control for differences in store price. Some stores might be higher priced in terms of all goods. Allow students about 15 minutes to solve this. To check assumptions, use sample proportions as estimators of population proportion: n1·p1 = 78·63/78 = 63 n1·q1 = 78·(1-63/78) = 15 n2·p2 = 82·49/82 = 49 n2·q2 = 82·(1-49/82) = 33 To check assumptions, use sample proportions as estimators of population proportion: n1·p1 = 78·63/78 = 63 n1·q1 = 78·(1-63/78) = 15 n2·p2 = 82·49/82 = 49 n2·q2 = 82·(1-49/82) = 33 9 To check assumptions, use sample proportions as estimators of population proportion: n1·p1 = 78·63/78 = 63 n1·q1 = 78·(1-63/78) = 15 n2·p2 = 82·49/82 = 49 n2·q2 = 82·(1-49/82) = 33 11 12 11 To check assumptions, use sample proportions as estimators of population proportion: n1·p1 = 1500·74/1500 = 74 n1·q1 = 1500·(1-74/1500) = 1426 n2·p2 = 1500·129/1500 = 129 n2·q2 = 1500·(1-129/1500) = 1371 15 16 15 If no estimate of p1 and p2 is available use p1=p2=.5 No estimate of p1 and p2 is available so use p1=p2=.5 As a result of this class, you will be