Question: 16 Sulfur compounds cause “off-odors” in wine, so winemakers want to know the odor thresh-hold, the lowest concentration of a compound that the human nose can detect. The odor threshold for dimethyl sulfide (DMS) in trained wine tasters is about 25 micrograms per liter of wine ( µg/l). The untrained noses of consumers may be less sensitive, however. Below are the DMS odor thresholds for 10 untrained students.

31, 31, 43, 36, 23, 34, 32, 30, 20, 24

Assume that the standard deviation of the odor threshold for untrained noses is known to be σ = 7 µg/l.

a) Make a stem plot to verify that the distribution is roughly symmetric with no outliers. (More data confirm that there are no systematic departures from Normality)

b) Give a 95% confidence interval for the mean DMS odor threshold among all students. (It is suggested that SPSS be used to solve this problem)