Assignment:
Q1: Companies are spending more time screening applicants than in the past. A study of 102 recruiters conducted by Execunet found that 77 did internet research on candidates.
a) Construct a 95% confidence interval estimate of the population proportion of recruiters who do internet research on candidates.
b) Based on (a) is it correct to conclude that more than 70% of recruiters do internet research on candidates.
Q2: A manufacturing company produces electrical insulators. If the insulators break when in use, a short circuit is likely to occur. To test the strength of insulators, destructive testing is carried out to determine hoe much force is required to break the insulators. Force is measured by observing the number of pounds of force applied to the insulator before it breaks. The following data are from 30 insulators object to this testing.
1870 - 1728 - 1656 - 1610 - 1634 - 1784 - 1522 - 1696 - 1592 - 1662
1866 - 1764 - 1734 - 1662 - 1734 - 1774 - 1550 - 1756 - 1762 - 1866
1820 - 1744 - 1788 - 1688 - 1810 - 1752 - 1680 - 1810 - 1652 - 1726
a) at the 0.05 level of significance, is there evidence that the mean force is greater than 1500 pounds?
b) What assumption must hold in order to perform the test in (a)
Q3: The manager of computer operations of a large company wants to study computer usage of two departments within the company - the accounting department and the research department. A random sample of five jobs from the accounting department in the past week are selected and the processing time for each job is recorded
Department Processing time
Accounting 9 3 8 7 12
Research 4 13 10 9 9 6
Use a level of significance of 0.05
a) Is there evidence that the mean processing time in the research department is greater than 6 seconds?
b) Is there evidence of a difference between the variance in the processing time of the two departments?
Q4: The following data represent the nationwide highest yield of different type of accounts
Money market 6Month CD 1-YR CD 1.5YR CD 5YR CD
4.55 4.75 4.94 4.95 5.05
4.50 4.70 4.90 4.91 5.05
4.40 4.69 4.85 4.85 5.02
4.38 4.65 4.84 4.82 5.00
4.38 4.65 4.85 4.80 5.00
a) At the 0.05 level of significance, is there evidence of a difference in the mean yields of the different accounts
Q5: A company that produces and markets videotaped continuing education programs for the financial industry has traditionally mailed sample tapes that contain previews of the programs to prospective customers. Customers then agree to purchase the program tapes or return the sample tapes. A group of sales representatives studied how to increase sales and found that many prospective customers believed it was difficult to tell from a sample tape alone whether the educational programs would meet their needs. The sales representatives performed an experiment to test whether sending the complete program tapes for review by customers would increase sales. They selected 80 customers from the mailing list and randomly assigned 40 to receive the sample tapes and 40 to receive the full program tapes for review. They then determined the number of tapes that were purchased and returned in each group. The results of the experiment are as follows:
ACTION SAMPLE FULL TOTAL
Purchases 6 14 20
Returned 34 26 60
Total 40 40 80
a) At the 0.05 level of significance, is there evidence of a difference in the proportion of tapes purchased on the basis of the type of tape sent to the customer?