Flashcards in Ch. 6 (Statistical Process Control-SPC) Deck (13)

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1

## Statistical process control (SPC)

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Statistical process control (SPC)

A process used to monitor standards by taking measurements and corrective action as a product or service is being produced.

2

## Control chart

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Control chart

A graphical presentation of process data over time.

3

## Natural variations

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Natural variations

Variability that affects every production process to some degree and is to be expected; also known as common cause.

4

## Assignable variation

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Assignable variation

Variation in a production process that can be traced to specific causes.

5

## x-bar chart

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x-bar chart

A quality control chart for variables that indicates when changes occur in the central tendency of a production process.

6

## R-chart

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R-chart

A control chart that tracks the “range” within a sample; it indicates that a gain or loss in uniformity has occurred in dispersion of a production process.

7

## Central limit theorem

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Central limit theorem

The theoretical foundation for x-bar charts, which states that regardless of the distribution of the population of all parts or services, the distribution of x-bars (averages) tends to follow a normal curve as the number of samples increases.

8

## calculate standard deviation

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1. find average of the sample means. = x-dblbar

2. UCL: add 3*(1/sqrt(N))

3. LCL: subtract 3*(1/sqrt(N))

4. Plot points

9

## calculate standard deviation with range values

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1. find average of the sample means. = x-dblbar

2. 2. UCL: add (A2 based on sample size*range mean)

3. LCL: subtract (A2 based on sample size*range mean)

4. Plot points

10

## calculate R-chart limits

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UCL: d4*R-bar

Mean: R-bar

LCL: d3*R-bar

11

## percent defective- p-chart

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1. calculate mean of defectives. p-bar

2. p-bar*(1 - p-bar)

3. divide by size of each sample (100 data in one sample)

4. sqrt root of everything

5. multiply by 3 and add to/subtract from p-bar for UCL/LCL

12

## number of defective- c-chart

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1. average of complaints. c-bar

2. add or subtract 3*sqrt(c-bar)

13