A manufacturing company produces steel housings for electrical equipment. The ma

Question

A manufacturing company produces steel housings for electrical equipment. The main component part of housing is a steel trough that is made out of a 14-guage steel coil. It is produced using a 250-ton progressive punch press with a wipe-down operation that put two 90-degree forms in the flat steel to make the trough. The distance from one side of the form to the other is critical because of the weatherproofing in outdoor applications. The widths (in inches) is stored in the file TROUGH from a sample of 49 troughs follows:

8.312 8.343 8.317 8.383 8.348 8.410 8.351 8.373 8.481 8.422 8.476 8.382 8.484 8.403 8.414 8.419 8.385 8.465 8.498 8.447 8.436 8.413 8.489 8.414 8.481 8.415 8.479 8.429 8.458 8.462 8.460 8.444 8.429 8.460 8.412 8.420 8.410 8.405 8.323 8.420 8.396 8.447 8.405 8.439 8.411 8.427 8.420 8.498 8.409

a. Construct a 95% confidence interval estimate of the mean width of the troughs. Use Minitab

b. Interpret the interval developed in (a).

Explanation / Answer

(a)

Following is the output of 95% confidence interval:

The required confidence interval is (8.4077, 8.4341).

(b)

We are 95% confident that the true mean width of the troughs is lies in the interval (8.4077, 8.4341).

Confidence interval - mean 95% confidence level 8.4209 mean 0.0461 std. dev. 49 n 2.011 t (df = 48) 0.0132 half-width 8.4341 upper confidence limit 8.4077 lower confidence limit

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