Rainfall and desert ants. Refer to the Journal of Biogeography (Dec. 2003) study of ants and their habitat in the desert of Central Asia, presented in Exercise 2.68

(p. 91). Recall that botanists randomly selected five sites in the Dry Steppe region and six sites in the Gobi Desert where ants were observed. One of the variables of interest is the annual rainfall (in millimeters) at each site. Summary statistics for the annual rainfall at each site are provided in the SAS printout below.

a. Give a point estimate for the average annual rainfall amount at ant sites in the Dry Steppe region of Central Asia.

b. Give the t-value used in a small-sample 90% confidence interval for the true average annual rainfall amount at ant sites in the Dry Steppe region.

c. Use the result you obtained in part b and the values of x and s shown on the SAS printout to form a 90% confidence interval for the target parameter.

d. Give a practical interpretation for the interval you found in part c.

e. Use the data in the ANTS file to check the validity of the confidence interval you found in part c.

f. Repeat parts a–e for the Gobi Desert region of Central Asia.

Transcribed Image Text:

The MEANS Procedure Analysis Variable: RAIN Mean 183.4000000 N REGION Obs DryStepp 5 Gobi 6 110.0000000 Std Dev 20.6470337 15.9749804