Statistical Analysis Review III: Confidence Intervals and Hypothesis Testing - Prof. Dongm, Study notes of Statistics

Download Statistical Analysis Review III: Confidence Intervals and Hypothesis Testing - Prof. Dongm and more Study notes Statistics in PDF only on Docsity! STA 2122 REVIEW III 1. True/False _____ The width of a confidence interval increases as the sample size decreases, everything else held constant. _____ It is desirable for the width of a confidence interval to be large. _____ A type I error is committed whenever the null hypothesis is incorrectly rejected. _____ For an upper-tailed hypothesis test, if the critical value of z is 2.33 and the test statistic is 2.57, the null hypothesis should be accepted. 2. If a 90% confidence interval for p is (.35, .45), what is meant by “90% confidence”? 3. In a random sample of 150 clerical workers, 30 exhibit an intense dislike for their jobs. Calculate a 94% confidence interval for the proportion of clerical workers who exhibit an intense dislike for their jobs. 4. A telephone answering service records the length of each call. A random sample of 12 reports yields a mean length of 3.2 minutes with a standard deviation of .7 minute. Calculate a 95% confidence interval for the mean length of phone calls for this answering service. 5. A market research firm wishes to determine the mean number of hours families in a particular community watch television per week. A random sample of 300 families results in a mean viewing time of 26.8 hours with a standard deviation of 7.3. Do you have enough evidence to conclude the mean viewing time in this community exceeds 25 hours? Use α = .07. 6. Define a Type I and Type II error in terms of problem # 5. 7. In a random sample of 200 college students, 45 had taken Statistics in high school. Using α = .04, do you have enough evidence to conclude the proportion of college students who have not taken Statistics in high school differs from .75? 8. Find the p-value for problem #7.