Methods and formulas for Moving Average Chart

Select the method or formula of your choice.

Plotted points

when i v
when i > v

Notation

TermDescription
vnumber of sample means that are averaged
μprocess mean
kparameter for Test 1. The default is 3.
σprocess standard deviation
nisize of subgroup i

Center line

The center line represents the process average. Minitab uses to estimate μ.

Control limits

Lower control limit (LCL)

when
when

Upper control limit (UCL)

when
when

Notation

TermDescription
nisize of subgroup i
vnumber of sample means that are averaged
μprocess mean
kparameter for Test 1. The default is 3.
σprocess standard deviation

Methods and formulas for Box-Cox

Box-Cox formula

If you use a Box-Cox transformation, Minitab transforms the original data values (Yi) according to the following formula:

where λ is the parameter for the transformation. Minitab then creates a control chart of the transformed data values (Wi). To learn how Minitab chooses the optimal value for λ, go to Methods and formulas for Box-Cox Transformation.

Common λ values

The following table shows some commonly used λ values and their transformations.
λ Transformation
2
0.5
0
−0.5
−1
By using this site you agree to the use of cookies for analytics and personalized content.  Read our policy