17.8 Does polyester decay? How quickly do synthetic fabrics such as polyester decay in landfills? A researcher buried 10 strips of polyester fabric in well-drained soil in the sum mer. Five of the strips, chosen at random, were dug up after 2 weeks; the other 5 were dug up after 16 weeks. Breaking strength is easy to measure and is a good indicator of decay. Lower strength means the fabric has decayed. Here are the breaking strengths in pounds:'

Sample 1 (2 weeks) j 118 126 126 120 129 Sample 2 (16 weeks) I 124 98 110 140 110 Figure 17.5 shows output for the two-sample t test using Option 1. (This output is from software that does Option 1 without rounding or truncating the degrees of freedom.) Do polyester strips buried for 16 weeks have significantly lower mean breaking strength than those buried for 2 weeks? Using the output in Figure 17.5, write a summary in a sentence or two, including t, df, P, and a conclusion.

17.9 Do good smells bring good business? Businesses know that customers often respoiad to background music. Do they also respond to odors? Spread a relaxing lavender odor through a small restaurant on one Saturday evening and do nothing on another evening.

Table 17.2 gives the time (minutes) that samples of 30 customers spent in the restaurant and the amount they spent (in euros).^ The two evenings were comparable in many ways (weather, customer count, and so on), so we ate willing to regard the data as independent SRSs from spring Saturday evenings at this restaurant.

(a) Does a lavender odor encourage customers to stay longer in the restaurant? Examine the time data and explain why they are suitable for two-sample t procedures. Use the two-sample t test to answer the question posed.

(b) Does a lavender odor encourage customers to spend more while in the restaurant?
Examine the spending data. In what ways do these data deviate from Normality?
With 30 observations, the t procedures are nonetheless reasonably accurate. Use the two-sample t test to answer the question posed.

NO ODOR TABLE 17.2 Time (minutes) and spending (euros) by restaurant customers LAVENDER MINUTES EUROS SPENT MINUTES EUROS SPENT 103 15.9 92 21.9 68 79 18.5 126 18.5 15.9 114 22.3 106 18.5 106 21.9 72 18.5 89 18.5 121 21.9 137 24.9 92 15.9 93 18.5 84 15.9 76 22.5 72 15.9 98 21.5 92 15.9 108 21.9 85 15.9 124 21.5 69 18.5 105 18.5 73 18.5 129 25.5 87 18.5 103 18.5 109 20.5 107 18.5 115 18.5 109 21.9 91 18.5 94 18.5 84 15.9 105 18.5 76 15.9 102 24.9 96 15.9 108 21.9 107 18.5 95 25.9 98 18.5 121 21.9 92 15.9 109 18.5 107 18.5 104 18.5 93 15.9 116 22.8 118 18.5 88 18.5 87 15.9 109 21.9 101 25.5 97 20.7 75 12.9 101 21.9 86 15.9 106 22.5