Number of nonconformities observed in 26 successive samples of 100 printed circuit boards. Sample 6 and 20 are out of control limits. Sample 6 was examined by a new inspector and he did not recognize several type of nonconformities that could have been present. Furthermore, the unusually large number of nonconformities in sample 20 resulted from a temperature control problem in the wave soldering machine, which was subsequentely repaired. The last 20 samples are further samples collected on inspection units (each formed by 100 boards).
Format
A data frame with 46 observations on the following 4 variables:
- x
Number of defectives in 100 printed circuit boards (inspection unit)
- sample
Sample ID
- size
Sample size
- trial
Trial sample indicator (TRUE/FALSE)
References
Montgomery, D.C. (1991) Introduction to Statistical Quality Control, 2nd ed, New York, John Wiley & Sons, pp. 173--175
Examples
data(circuit)
attach(circuit)
summary(circuit)
#> x sample size trial
#> Min. : 5.00 Min. : 1.00 Min. :100 Mode :logical
#> 1st Qu.:16.00 1st Qu.:12.25 1st Qu.:100 FALSE:20
#> Median :19.00 Median :23.50 Median :100 TRUE :26
#> Mean :19.17 Mean :23.50 Mean :100
#> 3rd Qu.:22.00 3rd Qu.:34.75 3rd Qu.:100
#> Max. :39.00 Max. :46.00 Max. :100
boxplot(x ~ trial)
plot(x, type="b")
detach(circuit)