Quality reporting point X-Bar Chart sample size results in last charted value drop significantly

https://schneiderampla.atlassian.net/browse/CE-1891

[System Info]
Ampla Versions: 6.5MR1
Operating System:Windows 2012 Server R2

[Raised by]
Customer Company: Royhill
CF Status: Standard
Customer Contact: kehgan.hau@royhill.com.au
SR Reference: 951179469

[Problem Summary]
Quality reporting point X-bar chart has rule of "Sample Size" value between 2-25. take 2 as an example, when only one sample is left for charting, the mean value is divided by 2 anyway, which is cause a significant value drop simply because the number of samples does not meet "Sample size". As regards of this, customer suggest:
1. allow user to set minimum sample size as "1" one.
2. any samples in a sample group does not meet "sample size" should be excluded from charting, because it does not represent the real quality expectation and observation.

Customer Original Comment:
x-bar charts should be able to have n=1 (ie: becomes an individuals chart).

x-bar charts are able to select whether the standard deviation is Root Mean Square (like in Excel) or are a Schewhart standard deviation, which is an unbiased estimation of a standard deviation.

x-bar charts where n>=2 should not display samples that have less that n samples in it, so the last value on the chart doesn’t become an outlier

[Workaround]
n/a

[What is the impact to Customer/s]
a significant value drop in chart does not represent real quality value observation.

[how to reproduce]
Check attached screen shot as it explains itself.