Circuit boards data

Number of nonconformities observed in 26 successive samples of 100 printed circuit boards. Sample 6 and 20 are outside the 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 subsequently repaired. The last 20 samples are further samples collected on inspection units (each formed by 100 boards).

Usage

data(circuit)

Format

A data frame with 46 observations on the following 4 variables.

sample

sample number

x

number of defectives in 100 printed circuit boards (inspection unit)

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)
describe(circuit, by = trial)
#> ── trial = FALSE ─────────────────────────────────────────────────────────────── 
#>        Obs  Mean StdDev Min Median Max
#> sample  20  36.5  5.916  27   36.5  46
#> x       20  18.3  4.714   9   18.5  28
#> size    20 100.0  0.000 100  100.0 100
#> 
#> ── trial = TRUE ──────────────────────────────────────────────────────────────── 
#>        Obs   Mean StdDev Min Median Max
#> sample  26  13.50  7.649   1   13.5  26
#> x       26  19.85  7.165   5   19.0  39
#> size    26 100.00  0.000 100  100.0 100
boxplot(x/size ~ trial, data = circuit)

plot(x/size ~ sample, data = circuit, type="b")