Business Statistics

648 Business Statistics

(using range) produced using SPSS will appear on the screen (Figure 17.4). From Charts, click X-

Bar and standard deviation/OK; the SPSS produced

x

control chart (using standard deviation) will

appear on the screen (Figure 17.5).

17.6.4 R Chart

The

x

chart is used to plot location values whereas the R chart is used to plot sample ranges. R charts

are used to control the variability in the quality of a product. In an R chart, the centre line is the aver-

age of sample range and is generally denoted by

.R

The lower control limit (LCL) is determined by

using the formula D

3

.R

. D

3

is a constant that depends on the sample ...