The manager of a computer retails store is concerned that hissuppliers have been giving him laptop computers with lower thanaverage quality. His research shows that replacement times for themodel laptop of concern are normally distributed with a mean of 4years and a standard deviation of 0.4 years. He then randomlyselects records on 49 laptops sold in the past and finds that themean replacement time is 3.8 years.
Assuming that the laptop replacement times have a mean of 4 yearsand a standard deviation of 0.4 years, find the probability that 49randomly selected laptops will have a mean replacement time of 3.8years or less.
P(M < 3.8 years) =Â Â
Enter your answer as a number accurate to 4 decimal places. NOTE:Answers obtained using exact z-scores or z-scoresrounded to 3 decimal places are accepted.
Based on the result above, does it appear that the computer storehas been given laptops of lower than average quality?
- Yes. The probability of this data is unlikely to have occurredby chance alone.
- No. The probability of obtaining this data is high enough tohave been a chance occurrence.
