The service life of a battery used in a cardiac pacemaker is assumed to be norma

Question

The service life of a battery used in a cardiac pacemaker is assumed to be normally distributed. A random sample of ten batteries is subjected to an accelerated life test by running them continuously at an elevated temperature until failure, and the following lifetimes (in hours) are obtained: 25.5, 26.1, 26.8, 23.2, 24.2, 28.4, 25.0, 27.8, 27.3, and 25.7.

(a) The manufacturer wants to be certain that the mean battery life exceeds 25 h. What conclusions can be drawn from these data (use = 0.05)?

(b) Construct a 90% two-sided confidence interval on mean life in the accelerated test.

(c) Construct a normal probability plot of the battery life data. What conclusions can you draw?

Explanation / Answer

a)

The One sample t-test and will be testing for greater than the hypothesized mean.
P-value = .042.

We can reject the null hypothesis that the mean is 25 for the alternative of mean > 25.

(b)

One sample t-test. Hypothesized mean of 25.

Confidence internal of 90 is not equal.

Answer: (25.058, 26.942)

(c)

The plotted points fall approximately along a straight line, so the assumption that battery life is normally distributed is appropriate.

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