Statistical Quality Control Practice Test 4

1. If x_i=total number of nonconformities in a sample of n_i inspection units, and there are N samples of different sample size, and x varies according to a Poisson distribution, what will be the value of center line of the u-chart?

\(\bar{u} = \frac{\sum_{i=1}^N \frac{x_i}{n_i}}{2N}\)

\(\bar{u} = \frac{\sum_{i=1}^N \frac{2x_i}{n_i}}{N}\)

\(\bar{u} = \frac{\sum_{i=1}^N \frac{x_i}{2n_i}}{2N}\)

\(\bar{u} = \frac{\sum_{i=1}^N \frac{x_i}{n_i}}{N}\)

2. Variable control charts can also be applied on attributes but their efficiency will be less as compared to the attribute control charts.

False

True

3. The Shewhart control charts for sample size n=1 are called _________

Stationary control charts

Control charts for individual measurements

Control charts for zero variance

Single Sample control charts

4. LCL for any p chart when the standard values are given are ________

LCL=\(p-3\sqrt[3]{\frac{p(1-p)}{n}}\)

LCL=\(p+\sqrt[3]{\frac{p(1-p)}{n}}\)

LCL=\(p-\sqrt{\frac{p(1-p)}{n}}\)

LCL=\(p+3 \sqrt{\frac{p(1-p)}{n}}\)

5. The c charts are also called _________

The control chart for nonconformities

Control charts for conformities per unit

Control chart for process mean

Control charts for fraction nonconforming

6. If the probability of a unit being conforming or nonconforming, depends on the previous unit being conforming or nonconforming, can p-chart be applied on the process?

This depends on the operator changes

Yes

This depends on the sample size

7. Which of these is not an assumption of the c-chart?

Number of potential locations for nonconformities should be large

Probability of occurrence of nonconformities should be small

Probability of occurrence of nonconformities should be constant

Probability of occurrence of nonconformities should be variable

8. When the Lower control limits for a p chart are less than zero, what is done?

LCL=0 is taken and assumed that control chart only has the upper control limit

The value LCL<0 is utilized in control chart

There is certain constant value added to LCL only, i.e. LCL_new=LCL_old+C

There is a certain constant C added to both UCL and LCL, i.e. UCL_new=UCL_old+ C and LCL_new=LCL_old+C

9. A type II error is also called a ___________

∅ Error

β Error

α Error

δ Error

10. The center line for any individuals control chart represents the value equal to __________

The mean of moving ranges

The process standard deviation

The moving range

The process mean