The Forest Management Institute is conducting a test, which involves measuring the size of trees by photographing from helicopter rather than actual field measurement. This process is especially important in forest areas accessible only by helicopter. A sample of 31 trees measured by aerial photography had a sample standard deviation of 2.24 . A 95 percent confidence interval for the population variance is represented by the values:
a. 30(2.24) / 46.979 and 30(2.24) / 16.791.
b. 30(2.242) / 46.979 and 30(2.242) / 16.791.
c. 31(2.24) / 16.791 and 31(2.24) / 46.979.
d. 31(2.242) / 46.979 and 31(2.242) / 16.791.
e. 30(2.24) / 16.791 and 30(2.24) / 46.979.
Question 2
Lily Energy Systems manufactures wood-burning heaters and fireplace inserts. One of its systems has an electric blower, which is thermostatically controlled. The blower is designed to automatically turn on when the temperature in the stove reaches 125 degrees F. and turn off at 85 degrees F. Complaints from customers indicate that the thermostat control is not working properly. The company feels that the thermostat is acceptable if the variance in the cutoff temperature is less than or equal to 175 . The company takes a sample of 24 thermostats and finds that the variance equals 289 . The calculated chi-square test statistic and the table value for a 0.05 significance level are:
a. 35.172, 38.99.
b. 37.983, 35.172.
c. 38.076, 38.99.
d. 37.983, 38.076.
e. none of these.
Laboratory, Institute of Biochemistry, University of Cologne.
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