I am trying to submit my answers for my stats class. I will post the problem, my

Question

I am trying to submit my answers for my stats class. I will post the problem, my solution/how I worked it on by hand, then how I did it on Minitab. I am getting two different answer sets, and I want to know which is right. I'm leaning on my own, but I'm still unsure. The answers have to be rounded to two decimal places and rounding only takes place at the end of all the calculations, never during the beginning. And the consonants in this case are determined off of a chart when the subgroup is 5 (such as in this problem set). I will also post the chart that I used. Please tell me if I am right or if the Minitab solution is right.

My solution by hand:

Minitab Solution:

And here is the chart of consonants, I've highlighted the values from the row I've used.

Please remember rounding is to be done at the end and to two decimal places.

Please let me know whether or not my solution is correct. Thank you.

The following samples have been taken from an on-going process. Use these values to create both an X bar and an R chart, and then answer the questions below. Sample 1: 56 48 53 58 52 Sample 2: 50 59 57 54 54 Sample 3: 61 59 56 55 58 Sample 4: 57 51 47 57 50 Sample 5: 50 49 57 55 56 Sample 6: 56 55 60 58 54 1) What is the value of the centerline for an X bar chart? (Round to two decimal places) 54.73 2) The upper control limit for the X bar chart is: = 54.73333 +(0.577 x 8.166667) = 59.445496859-59.45

Explanation / Answer

THe solution by hand is correct because the method of finding control limits based on all the values in the groups

also the formulae used in the calculation with n = 5 are correct.

But minitab used different method and not regular methods

It is easy to obsered that from the central limit of X bar chart.

By hand the mean is 54.73 and using minitab the mean is 55.06 whic is different from 54.74.

So control limits calculated by hand are more accurate than minitab.

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