The rapid evolution of computer hardware and software has made it easy for businesses to conduct computer-based and Web-based (i.e., electronic) surveys. Professors at Michigan State and DePaul Universities collaborated on a study designed to compare the response rates of electronic surveys and traditional print surveys (Decision Sciences Institute, Decision Line, July 2001). The two surveys were developed for customers who had purchased products over the Internet from a leading retailer of office supplies. Of the 631 customers mailed the printed survey, 261 returned usable responses. Of the 414 customers who were sent a computer disk with the electronic survey, 155 returned usable responses.
a. Estimate the difference between the responses rates of the two survey types using a 90% confidence interval Interpret the result.
b. If the difference in response rates is 5% or less, the researchers will infer that there is no "practical" difference in response rates for the two surveys. Are the researchers able to make this inference? Explain.