Dullco 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:
select one:
a. -2.101
b. -1.980
c. -1.960
d. -1.728

lyrics d  - 1.782

Step-by-step explanation:

Assume Normal Distribution

we have  μ₀ = 40       (from Dullco claims)

And from sample   μ  = 37.8    and standard deviation of  5.4

random sample n = 18

We have to use t-student for testing the hypothesis

and we have a one tail test (left) since Dullco claims : " at least"  meaning (always bigger or at least ) not different.

Then

t (s) =( μ -  μ₀) / (σ/√n)   ⇒ t (s) = [(37.8  - 40 )* √18 ]/5.4

t (s) = - 1.7284

283 square feet

step-by-step explanation:

good luck

answer: ♡♡♡♡♡♡♡♡♡♡

step-by-step explanation: