Life tests performed on a sample of 13 batteries of a new model indicated: (1)an average life of 75 months, and (2)a standard deviation of 5 months.Other battery models, produced by similar processes, have normally distributed life spans.The 98% confidence interval for the population mean life of the new model is _________.
A)63.37 to 86.63
B)61.60 to 88.41
C)71.77 to 78.23
D)71.28 to 78.72
E)79.86 to 81.28

Question

Quizplus · Accepted Answer

The 98% confidence interval is calculated using the formula: mean ± (z * (standard deviation/√n)). For a 98% confidence level and a sample size of 13, the z-value is approximately 2.576. Plugging in the values: 75 ± (2.576 * (5/√13)) gives the interval 71.28 to 78.72.

Life Tests Performed on a Sample of 13 Batteries of a New