23 Advanced Control Charts

Question 1

**X-bar R Charts
are used for which data?

Answer 1

• Variable, continuous data that can be grouped into subgroups to chart their means
• Subgroups with <8 data counts each
• Sigma CAN NOT be calculated easily
• The x-bar chart plots the subgroups means
• The R chart plots the range**

Question 2

**X-bar S Charts
are used for which data?

Answer 2

• Variable, continuous data that can be grouped into subgroups, allowing to chart their means
• **Subgroups hold >8 data counts **
• Sigma’s easily calculated
• The x-bar chart plots the mean of each subgroup
• The S chart plots the std dev

Question 3

I-MR Charts
(individual moving range)
are used for which data?

Answer 3

• Variable, continuous data that CAN NOT be grouped into subgroups with means, so individual data points need to be tracked
• Data’s difficult / expensive to obtain

Question 4

P-Charts
are used for what?

Answer 4

Discrete data presented as percentage (that is defective)
Does NOT require a constant sample / subgroup size
Plots the PROPORTION of units that are nonconform
It’s impossible, very time-consuming or not feasible to measure / analyze numerical measurements

Question 5

NP-Charts
are used for what?

Answer 5

Discrete data presented as percentage (that is defective)
Does NOT require a constant sample / subgroup size
Plots the NUMBER of units that are nonconform
It’s impossible, very time-consuming or not feasible to measure / analyze numerical measurements

Question 6

U-Charts
are used for what?

Answer 6

Discrete data presented as count (number of defects)
Does NOT require a constant sample / subgroup size
Plots the number of defects PER UNIT
Used when data is about the defects themselves, not the overall defective product

Question 7

C-Charts
are used for what?

Answer 7

Discrete data presented as count (number of defects)
DOES REQUIRE a constant sample / subgroup size
Plots the number of defects PER SAMPLE
Used when data is about the defects themselves, not the overall defective product