Question

Determine the % change impact in relation with the sample standard deviation.
On the 9th month a new inspection was implemented to improve consistency.Prepare Time Series Chart.
Month	Values
1	129
2	128
3	180
4	138
5	156
6	156
7	134
8	175	Change
9	160
10	175
11	169
12	170

Answer 1

The time series chart is given below:

The % change impact in relation with the sample standard deviation can be calculated as:

So, YES, as the standard deviation reduced by 69.42% after the 9th month,
the new inspection that was implemented certainly improved consistency.

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