The manager of quality assurance for a division that produces hair dryers is int

Question

The manager of quality assurance for a division that produces hair dryers is interested in the average number of switches that can be tested by the division’s employees. Assuming that the number of switches that are tested each hour by an employee follows a normal distribution (centred at µ), the manager wants to estimate µ with 90% confidence. Also, this estimate must be within one unit (switch) of µ. The manager estimates that H is 45 switches and L is 25 switches.

How large a sample will be necessary?

Explanation / Answer

here as assuming estimatiion is based on 2 std deviaiton away from mean ; therefore std deviaiton =(45-25)/4 =5

margin of error E =1

and for 90% CI ; z=1.6449

hence required sample size n=(z*Std deviaiton/E)2 =~68

please revert for any clarification requied,

Note: I have assumed estimation is 2 std deviaiton away as no prior information is given.

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