Question

4. A manufacturing firm claims that the batteries used in their electronic games will last an average of 30 hours. To maintain this average, 16 batteries are tested each month. If the computed t-value falls between – ?!.!"# and ?!.!"#, the firm is satisfied with its claim. Should they be satisfied if they test asample that has a mean of ? = 27.5 hours and a standard deviation of ? = 5 hours? Assume the distribution of battery lives to be approximately normal.

Answer 1

Solution :

= 30

=27.5

S =5

n = 16

This is the two tailed test .

The null and alternative hypothesis is ,

H0 :    = 30

Ha :     30

Test statistic = t

= ( - ) / S / n

= (27.5 -30 ) / 5 / 16

= -2.0

Test statistic = t = -2.0

P-value = 0.0639