4. According to the Chebyshev rule, at least 75% of all observations in any data set are contained within a distance of how many standard deviations around the mean? (A) 1 (B) 2 (C) 3 (D) 4

9. A manufacturer wants to increase the shelf life of a line of cake mixes. Past records indicate that the average shelf life of the mix is 216 days. After a revised mix has been developed, a sample of nine boxes of cake mix gave these shelf lives (in days): 215, 217, 218, 219, 216, 217, 217, 218 and 218. At the 0.025 level, has the shelf life of the cake mix increased? (A) Yes, because computed t is greater than the critical value. (B) Yes, because computed t is less than the critical value. (C) No, because computed t lies in the region of acceptance. (D) No, because 217.24 is quite close to 216.

4. According to the Chebyshev rule, at least 75% of all observations in any data set are contained within a distance of how many standard deviations around the mean?
(A) 1
(B) 2
(C) 3
(D) 4

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