Lots-o-Letters
Speaking of Groups
Math
Randoms
100
This letter is used to represent the sample size of each sample group

n

100

0 is typically the lower control limit for the R-chart when...

the subgroup size is small (less than 7)

100

What is the mean, median, mode of:

2, 6, 8, 25, 6

23.5, 6, 6

100
When C(sub p) = C(sub pk) the data is...

centered

200

These two, three-letter items represent the engineered tolerance.

USL / LSL

200

Does an X - MR chart have groups/subgroups?

No

200

What is the range of:

1, 5, 7, 13, 7, 9, 5

12

200
A Capability index that is most desirable is...

Over 1

300

This letter represents the centerline of the X-bar chart.

X-Double Bar

300

What would you use to evaluate/measure the dispersion of data points of a process?

Standard deviation / Range (more typically Sd)

300

Find the average of:

2, 3, 5, 3, 3, 9, 4

29/7 4.14

300

What type of relationship has an "r" value of 0.966

Linear, very related and close to the linear line.

400

D2 (subscript 2) is...

One of Shewhart's constants

400

What are the three measures of central tendency?

Mean, Median, and Mode

400

A process is in control with a mean of 52 and a standard deviation of 2.  The upper specification for the product being produced is 60, and the lower specification is 42.  What is the value of C(pk)?

1.33

400

Why is a Median/range chart useful?

Less math

500

"X" represents...

an individual data value - specifically for X-bar or Md charts or similar

500

Why is 99.7% an important value?

For a process with normal statistical distribution and a mean of mu and standard deviation of sigma, it represents the percentage of data points within +/- 3 sigma.
500

What is the range of:

2, 4, 2, 3, 4, 5, 3, 5, 6

4

500

What does the Z-score allow us to do?

Z-score allows use to determine the area under a chart using the table in the book (know this part of the chapter for the test and how to use it!)

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