3. Each microdrill in a random sample 90 microdrills was used to drill holes in

Question

3. Each microdrill in a random sample 90 microdrills was used to drill holes in low-carbon alloy steel. The number of holes drilled before failure for each microdrill was recorded. The average number of holes drilled was 13 and the sample standard deviation was 6.73. a) [8 points] This is an example of which of the four cases discussed in class? (See presentation b) [8 points] If the example is changed so that the population standard deviation is known to c) [8 points] If the example is changed so that1) the parent population is normally notes on the class handout which is also on the class schedule.) be 6.4, this becomes an example of which case? distributed and (2) the sample size is 25, this becomes an example of which case?

Explanation / Answer

a)

To perform hypothesis test, we would be using the t-test over here since the sample std deviation is given

b)

If instead of sample std deviation, population std deviation is given, it would change to z-test wherein we use population std deviation

c)

In that case, we would still be using the t-test to test for the hypothesis

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