# The normal distribution can be used to calculate the

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16. The normal distribution can be used to calculate the confidence interval for the difference between population proportions as long as the sample sizes are at least 15 for each sample. True False
17. One method to obtain a narrower confidence interval with a given confidence level is to increase the sample size.
18. FalseMeasuring the effectiveness of a weight loss program by weighing members at the beginning and the end of the program is an example of independent samples.
19. If we are testing for the difference between the means of two independent samples from a normal population with samples of nx = 20 and ny = 20, the number of degrees of freedom for the t test statistic is equal to _____.
20. Two samples each of size 25 are taken from independent populations assumed to be normally distributed with equal variances. The first sample has a mean of 35.5 and standard deviation of 3.0 while the second sample has a mean of 33.0 and standard deviation of 4.0. The pooled variance estimate is ____ 3.5 18 12.5 7
21. Two samples each of size 25 are taken from independent populations assumed to be normally distributed with equalvariances. The first sample has a mean of 35.5 and standard deviation of 3.0 while the second sample has a mean of 33.0 and standard deviation of 4.0. The computed t statistic is _______.
22. Two samples each of size 25 are taken from independent populations assumed to be normally distributed with equal variances. The first sample has a mea n of 35.5 and standard deviation of 3.0 while the second sample has a mean of 33.0 and standard deviation of 4.0. Based on the data, the p-value for the F test of equal variances will be .166. Based on this p- value, is the assumption of equal variances correct?
23. To investigate the efficacy of a diet, a random sample of 16 male patients is drawn from a population of adult males using the diet. The weight of each individual in the sample is taken at the start of the diet and at a medical follow-up four weeks later. Assuming that the population of differences in weight before versus after the diet follow a normal distribution, the t-test for
related samples can be used to determine if there was a significant decrease in the mean weight during this period. Suppose the mean decrease in weights over all 16 subjects in the study is 3.0 pounds with the standard deviation of differences computed as 6.0 pounds. The critical value for a one-sided test of the mean difference at a 0.05 level of significance is _______.