Assignment

Question 1

A sample of 81 account balances of a credit company showed an average balance of $1,200 with a standard deviation of $126.

1 Formulate the hypotheses that can be used to determine whether the mean of all account balances is significantly different from $1,150.
2 Compute the test statistic.
3 Using the p-value approach, what is your conclusion? Let α = .05.

Question 2

During the recent primary elections, the democratic presidential candidate showed the following pre-election voter support in Alabama and Mississippi.

State Voters Surveyed Voters in favor of Democratic Candidate
Alabama 800 440
Mississippi 600 360

1 We want to determine whether or not the proportions of voters favoring the Democratic candidate were the same in both states. Provide the hypotheses.

2 Compute the test statistic.

3 Determine the p-value; and at 95% confidence, test the above hypotheses.

Question 3

In order to estimate the difference between the yearly incomes of marketing managers in the East and West of the United States, the following information was gathered.

East                                 West
n1 = 40                            n2 = 45
     = 72 (in $1,000)               = 78 (in $1,000)
s1 = 6 (in $1,000)             s2 = 8 (in $1,000)

1 Develop an interval estimate for the difference between the average yearly incomes of the marketing managers in the East and West. Use α = 0.05.

2 At 95% confidence, use the p-value approach and test to determine if the average yearly income of marketing managers in the East is significantly different from the West.