Durco manufacturing claims that its alkaline batteries last at least 40 hours on average in a certain type of portable cd player. but tests on a random sample of 18 batteries from a day's large production run showed a mean battery life of 37.8 hours with a standard deviation of 5.4 hours. to test dullco's hypothesis, the test statistic is
multiple choice
a. −1.980
b. −2.101
c. −1.960
d. −1.728

d. −1.728

Step-by-step explanation:

As per given , we have

Null hypothesis :

Alternative hypothesis :    (against Null hypothesis )

Alternative hypothesis is one-tailed , then the test is one-tailed test.

Sample size : n= 18

Sample mean :

Sample standard deviation : s= 5.4

Population standard deviation is unknown , so we should perform t-test.

Test statistic :

Substitute the values, we get

Hence, the test statistic is −1.728.

answer: the first graph

step-by-step explanation: