1) A light bulb producing company states that its lights will last an average of 1200 hours with a standard deviation of 200 hours. A sample of 100 light bulbs from the company were tested and the researcher found that the average life of each light bulb was 1050 hours. At a 95% confidence level, determine whether these light bulbs are in compliance with the company's claim.

Will someone tell me the formula or walk me through the steps of how to do this?

Question

1)  A light bulb producing company states that its lights will last an average of 1200 hours with a standard deviation of 200 hours.  A sample of 100 light bulbs from the company were tested and the researcher found that the average life of each light bulb was 1050 hours.  At a 95% confidence level, determine whether these light bulbs are in compliance with the company's claim.

Will someone tell me the formula or walk me through the steps of how to do this?

amistre64 · Answer

$$z=\frac{x-\bar x}{\sigma}$$
if the zscore associated with the numbers given falls within 45.5% either way of the mean.