What statistical test of differences is appropriate in the following situations?
a. Comparison of average campaign contributions (in $) of Democrats, Republicans, and Independents.
b. Advertising managers and brand managers have responded “Yes,” “No,” or “Not sure” to an attitude question. The advertising and brand managers’ responses are to be compared.
c. One-half of a sample received an incentive in a mail survey while the other half did not. A comparison of response rates is desired.
d. A researcher believes coupon links pushed through Facebook.com will generate more sales than coupon links pushed through Twitter.com.
e. A manager wishes to compare the job performance of a salesperson before ethics training with the performance of that same salesperson after ethics training.