In an automobile repair and service industry, the average number of defective items in all the lots of automobile parts produced by a machine last week was 8. The supervisor believes that the mean...

In an automobile repair and service industry, the average number of defective items in all the lots of automobile parts produced by a machine last week was 8. The supervisor believes that the mean number of defective parts produced by the same machine will differ in the present week.  To test whether the average differs from 8, he samples 30 lots to obtain the mean number of defective parts to be 9 with a standard deviation of 3.


Compute the value of the test statistic.

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