Question

A computer laboratory manager was in charge of purchasing new battery packs for her lab of laptop computers. She narrowed her choices to two models that were available for her machines. Since the models cost about the same, she was interested in determining whether there was a difference in the average time the battery packs would function before needing to be recharged. She took two independent samples and computed the following summary information: Battery Pack Model 1 Battery Pack Model 2Sample Size 9 9Sample Mean 5 hours 5.5 hoursStandard Deviation 1.5 hours 1.3 hoursUsing the null and alternate hypothesis:H0:mu1-mu2=0 vs. Ha: mu1-mu2 not equal 0Calculate the test statistic for this test.

Answer 1

-0.756

Explanation:

N1 = 9

N2 = 9

Sd1 = 1.5 hours

Sd2 = 1.3 hours

X1 = 5 hours

X2 = 5.5 hours

Hypothesis

H0: mu1 - mu2 = 0

H1 : mu1 - mu2 not equal to 0

Test statistic

t = (x1 - x2)/SE

SE is the standard error, which is unknown

SE = √sd1²/n1 + sd2²/n2

= √1.5²/9 + 1.3²/9

= √0.25+0.1878

= √0.4378

= 0.66166

t statistics = (5-5.5)/0.66166

= -0.5/0.66166

= -0.756