Question

A manufacturer of flashlight batteries took a sample of 13 batteries from a day’s production and used them continuously until they failed to work. The life lengths of the batteries, in hours, until they failed were: 342, 426, 317, 545, 264, 451, 1049, 631, 512, 266, 492, 562, and 298. At the .05 level of significance, is there evidence to suggest that the mean life length of the batteries produced by this manufacturer is more than 400 hours? A. Yes, because the test value 1.257 is less than the critical value 1.782 B. No, because the test value 1.257 is greater than the critical value 1.115 C. No, because the p-value for this test is equal to .1164 D. Yes, because the test value 1.257 is less than the critical value 2.179 Reset Selection

Answer 1

A:

Explanation:

***I'm pretty sure A should read "NO, because the test value 1.257 is less than the critical value 1.782. Please check the wording of the problem***

H0 : μ ≤ 400

Ha : μ > 400 (claim)

Sample mean: 6,155/13

Sample standard deviation: √44422.4359

Critical test value: t > 1.782

t = (6,155/13 - 400)/[(√44422.4359)/√13] = 1.257

1.257 < 1.782 ; we fail to reject the null hypothesis

There is not enough evidence at the 5% level of significance to support the claim that the mean battery life is at least 400 hours.