By law, the levels of toxic organic compounds in fish are constantly monitored. A technique, called matrix solid-phase dispersion (MSPD), has been developed for chemically extracting trace organic compounds from fish specimens (Chrornatographia, Mar. 1995). The MSPD method was tested as follows. Uncontaminated fish fillets were injected with a known amount of toxin.

The MSPD method was then used to extract the contammant and the percentage of the toxic compound recovered was measured. The recovery percentages for n = 5 fish fillets are listed below:

, Do the data provide sufficient evidence to indicate that the mean recovery percentage of the toxic compound exceeds 85% using the new MSPD method? Test using a = .05.

650 To instdl customer loyalty, airlines, hotels, rental car compames, and cred~t card companies (among others) have lnit~atedfrequency rnarketingprograrns that reward their regular customers. In the United States alone, 30 million people are members of the frequent flier programs of the a~rline mdustry (Fortune, Feb. 22,1993). A large fast-food restaurant chain wished to explore the profitability of such a program.They randomly selected 12 of their 1,200 restaurants nationwide and instituted a frequency program that rewarded customers with a $5.00 gift certificate after every 10 meals purchased at full price. They ran the trial program for three months.The restaurants not in the sample had an average increase in profits of $1,047.34 over the previous three months, whereas the restaurants in the sample had the following changes in profit:

Note that the last number is negative, representing a decrease in profits. Summary statistics and graphs for the data are given in the SPSS printout on page 326.

a. Specify the appropriate null and alternative hypotheses for determining whether the mean profit change for restaurants with frequency programs is significantly greater (in a statistical sense) than

$1,047.34.

b. Conduct the test of part b using a = .05. Does it appear that the frequency program would be profitable for the company if adopted nationwide?