Statistics

(1) Suppose a research firm conducted a survey to determine the average amount of money steady smokers spend on cigarettes during a week. A sample of 500 steady smokers revealed that the sample mean is $30 and the sample standard deviation is $8.00. What is the point estimate of the population variance?
(a) 30
(b) 40
(c) 8
(d) 64
(e) None of the above __________

(2) For a given level of confidence and sample size, what will happen to the confidence interval for the population mean as the population variance decreases?
(a) Remains the same
(b) Gets narrower
(c) Gets larger
(d) Cannot be determined
(e) None of the above __________

(3) Which statement is incorrect regarding the Student's t-distribution?
(a) Mean = 0
(b) Symmetric distribution
(c) Based on degrees of freedom
(d) There is only one distribution
(e) All of the above are correct __________

(4)The mean number of travel days per year for the outside salespeople employed by hardware distributors is to be estimated. The 0.90 degree of confidence is to be used. The mean of a small pilot study was 150 days, with a standard deviation of 14 days. If the population mean is to be estimated within two days, how many outside salespeople should be sampled?
(a) 134
(b) 452
(c) 511
(d) 1069
(e) None of the above
__________

(5) The claim that "40% of those persons who retired from an industrial job before the age of 60 would return to work if a suitable job was available" is to be investigated at the 0.02 level of risk. If 74 out of the 200 workers sampled said they would return to work, what is our decision?
(a) Do not reject the null hypothesis because -0.866 lies in the region between 0 and -2.58
(b) Do not reject the null hypothesis because -0.866 lies in the region between 0 and -2.33
(c) Reject the null hypothesis because 37% is less than 40%
(d) Do not reject the null hypothesis because 37% lies in the area between 0 and 40%
(e) None of the above __________

(6) Suppose that an automobile manufacturer designed a radically new lightweight engine and wants to recommend the grade of gasoline to use. The four grades are below regular, regular, premium, and super premium. The test car made three trial runs on the test track using each of the four grades. Assuming any grade can be used at the 0.05 level, what is the critical value of F?

Kilometers per liter
Below Super
Trial # Regular Regular Premium Premium
1 39.31 36.69 38.99 40.04
2 39.87 40.00 40.02 39.89
3 39.87 41.01 39.99 39.93
(a) 1.96
(b) 2.33
(c) 4.07
(d) 12.00
(e) None of the above is correct __________