The manager of a computer retails store is concerned that his suppliers have been giving him laptop computers with lower than average quality. His research shows that replacement times for the model laptop of concern are normally distributed with a mean of 4.4 years and a standard deviation of 0.5 years. He then randomly selects records on 37 laptops sold in the past. Round the answers of following questions to 4 decimal places. For 37 laptops, find the probability that the average replacement time is less than 4.5 year.  For part d), is the assumption of normal necessary? YesNo

Question

The manager of a computer retails store is concerned that his suppliers have been giving him laptop computers with lower than average quality. His research shows that replacement times for the model laptop of concern are normally distributed with a mean of 4.4 years and a standard deviation of 0.5 years. He then randomly selects records on 37 laptops sold in the past. Round the answers of following questions to 4 decimal places.

  1. For 37 laptops, find the probability that the average replacement time is less than 4.5 year. 
  2. For part d), is the assumption of normal necessary? YesNo

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