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

Question

The service life of a battery used in a cardiac pacemaker 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. The manufacturer wants to be certain that the mean battery life exceeds 25h. What conclusions can be drawn from the data (use a = 0.05)? Construct a 90% two-sided confidence interval on mean life in the accelerated test. Construct a normal probability plot of the battery life data. What conclusions can you draw?

Explanation / Answer

Solution:

a. For sample t-test ,

It will be testing for greater than hypothesized mean.

By calculating,we get the P-value = 0.042.

It can reject the null hypothesis ,so that the mean is 25 for the alternative of mean > 25.

b. For sample t-test.

It will be testing for greater than hypothesized mean.

If Confidence internal of 90 is not equal.

we get the values= (25.058, 26.942)

C. The plotted points fall approx. along the straight line, so the assumption of that battery life is normally distributed is appropriate.

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