1.If the sample correlation coefficient has a value different from z ero ( e.g., r 0.45), this automatically means that the correlation in the population is also different from zero. Is this statement correct? Explain.

2.A sample set of 30 scores has a mean equal to 82 and a standard deviation of 12. Can we reject the hypothesis that this sample is a random sample from a normal population with 85? Use 0.012 tail in making your decision.

3. Using each of the following random samples, determine the 95% and 99% confidence intervals for the population mean:

a.Xobt 25,s6,N15 b.Xobt 120,s8,N30

c. Xobt 30.6,s5.5,N24 d.Redo part a with N30. What happens to the

confidence interval as N increases?

4.A physician employed by a large corporation believes that due to an increase in sedentary life in the past decade, middle-age men have become fatter. In 1995, the cor poration mea sured t he p ercentage o f f at i n their employees. For the middle-age men, the scores were normally distributed, with a mean of 22%. To test her h ypothesis, t he ph ysician mea sures t he f at percentage in a random sample of 12 middle-age men currently employed by the corporation. The fat percentages found were as follows: 24, 40, 29, 32, 33, 25, 15, 22, 18, 25, 16, 27. On the basis of these data, can we conclude that middle-age men employed by the corporation have become fatter? Assume a direc- tional H1 is legitimate and use 0.051 tail in making

your decision.

5.A local business school claims that its graduating

seniors g et h igher-paying j obs t han t he nat ional average for business school graduates. Last year's figures for salaries paid to all business school grad- uates on their first job showed a mean of $10.20 per hour. A r andom sample of 10 graduates from last year's class of the local business school showed the following hourly salaries for their first job: $9.40, $10.30, $11.20, $10.80, $10.40, $9.70, $9.80, $10.60, $10.70, $10.90. You are skeptical of the business school claim and decide to e valuate the salary of the business school graduates, using 0.052 tail. What do you conclude?