Friday, August 21, 2015

Interpretation of X̄ & R charts:

Links to all courses
In order to judge if a process is in control, X̄ & R charts should be examined together and the process should be deemed in statistical control if both the charts show a state of control. Situations exists where R-chart is in a state of control but X̄ is not.
Given below are such situations:

Serial #
R-chart
Interpretation
1 In control Points beyond limits only on one side Level of process has shifted
2 In control Points beyond limits on both the side Level of process is changing in erratic manner –frequent adjustments.
3 Out of control Points beyond limits on both the side Variability has increased
4 Out of control Out of control on one side Both level and variability has changed
5 In control Run of 7 or more points on one side of central line Shift in process level
6 In control Trend of 7 or more points. No point outside control limits Process level is gradually changing
7 Run of 7 or more points above central line. --- Variability has increased
8 Points too close to the central line -- Systematic difference within sub-groups
9 ---- Points too close to the central line Systematic differences within sub-groups.

Source: Fundamentals of Applied Statistics, Gupta & Kapoor. 

No comments:
Write comments

Hey, we've a very popular astronomy portal in Bangla language. If You know Bangla, You'll like it - sky.bishwo.com
Join Our Newsletter