Confidence-interval with a margin for error

Reference no: EM1396887

A new brand of laptop battery is produced by ZELCO. The company claims that the battery will last for an extended period of time before a recharge is necessary. A sample of 40 batteries is tested for the length of usage time to recharge. The sample results are as follows:

Sample Size = 40
Sample Mean = 6.5 hrs.
Sample Standard Deviation = 1.3 hrs.

a. Construct a 99% confidence interval for the average length of usage time to recharge.

b. Interpret this interval.

c. How large a sample size will need to be selected if we wish to have a 99% confidence interval with a margin for error of .25 hours?

Reference no: EM1396887

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