Average chart

If action and warning limits are added to a moving average chart, they should be plotted at 31+Jn and 2l+Jn units of standard deviation, respectively. 

Figure 6.7 Data shown on (a) a Shewhart chart and (b) a moving average chart (n =4).

Figure SAQ 6.2 (a) Shewhart chart with warning and action limits at 2 and 3 standard deviations, respectively, (b) Moving average chart (n = 5) with warning and action limits at 2 Jn and 3 Jn standard deviations, respectively, (c) CUSUM chart, (d) CUSUM chart with V-mask.

A typical pair of Shewhart charts, (a) Averages chart and (b) ranges chart. Point A shows a lack of control of averages only, point B of ranges only and point C of both together. 

Control limits for the average chart will be drawn on the basis of specihc gravity done by QC at the time of bulk sample analysis prior to hlling. 

Starting with a hypothetical examination for a set of process DH color values, EWMA and control charting will be contrasted against conventional individual and modified moving range average charting techniques. 

Calculate the upper and lower control limits (UCL and LCL) for the average chart and the range chart these are the statistical signals that will show when the process is not running in its usual mode. Add the control limits to the charts (Exhibit 52.2). 

Molion (1975) employed climatological data (average charts of wind and specific humidity seasonal values) and the method of Penman (1963) to estimate that about 52% of the rain falling on the region was lost through the river. Similarly Villa Nova et al. (1976) applied Penman s method adapted to forested regions by Shiau and Davar (1973) and calculated that evaporation represented 54%, and 46% of rainfall was lost to the river. 

The example control charts presented by Besterfield in Fig. 2 demonstrate four major types of out-of-control patterns.f A fifth pattern is due to mistakes, which will usually show up as isolated, out-of-control points. All apply equally to production and sampling operations. All patterns may be observed on both range (R) charts and standard (or reference) process average charts but are usually more common to charts. 

An example of a Shewhart Chart is shown below for a hypothetical powder fill process. Five vials of product were sampled every hour and the net content of each vial was determined. The Shewhart Chart is shown in Fig. 1. The Average Chart indicates lack of statistical control at subgroups 3, 4, 9, 14, and 17. Further study of the Average Chart indicates a possible shift in the process mean at subgroup 12, and the Range Chart shows an increase at subgroup 6. Subsequent special cause investigation determined that the shift in process... 

The control chart limits for the Average Chart were ... 

Chart for Averages ( ) Chart for Range (R) Chart for Averages ( ) Chart for Standard Deviation (S) ... 

As the computed F statistics of the interaction DIET X EXR, that is F,. = 14.15 > 10.128 = Fo 05(1,3), we do have sufficient evidence to claim that two DIETs do affect WTLOSS differently at the two different levels of EXERCISE amount. It also suggests that SEX may have different WTLOSS. Further examination of the marginal average chart (see Figure 3) reveals that the male under this experimental setup attains greater WTLOSS than the female. It is noted that DIET 1 has effect on WTLOSS when it is used with a medium amount of EXERCISE. However, DIET 2 also produces a sizable WTLOSS when it is used with a higher amount of EXERCISE. 

Figure 3 Marginal Average Chart with 95% Confidence Level.

The EWMA Control Chart refers to the Exponentially Weighted Moving Average Chart. The common approach is plotting process data as a time series and... 

Figure 2. Shows 5-point moving average chart.

This pattern, then, is a blend of the weighting functions employed by the Shewhart Control Chart and the CUSUM Chart. We make use of all data points yet more emphasis is placed on the recent ones. Although the Stepwise SPC Chart is a combination of the Shewhart Control Chart and the CUSUM Chart, the Exponentially Weighted Moving Average Chart is a compromise of the two. Figure 6 illustrates the EWMA. 

CHART FOR AVERAGES CHART FOR STANDARD DEVIATIONS CHART FOR RANGES ... 

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