Aconsumers’ advocate group would like to evaluate the average energy efficiency (eer) of window mounted, large-capacity air conditioning units. a random sample of 36 units is selected and tested for a fixed period of time. their eer records are as follows: 8.9 9.1 9.2 9.1 8.4 9.5 9.0 9.6 9.3 9.3 8.9 9.7 8.7 9.4 8.5 8.9 8.4 9.5 9.39.3 8.8 9.4 8.9 9.3 9.0 9.2 9.1 9.8 9.6 9.3 9.2 9.1 9.6 9.8 9.5 10.0using the 0.05 level of significance, is there evi- dence that the average eer is different from 9.0?

Yes , there is evidence that the average EER is different from 9.0

Step-by-step explanation:

Summing up the samples given , we have 331.6

Therefore , sample mean = 331.6/36

≈9.2

The standard deviation is ≈ 0.38

Since n > 30 , then we use  Z- statistics

Let : Average EER = 9

: Average ≠ 9

using the z - formula

z =

=

= 3. 15

Checking the z- value at 0.05 , we have 1.64

Conclusion: since the z- calculate value is greater than the z-tab , then we reject the null hypothesis and conclude that there the average EER is different from 9