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).

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")