Chart Plotting Exercise (5)

We now have enough data to calculate the first moving range.

Module A6 A5            
Date Completed 20/8 21/8            
Actual 33.0 37.5            
Estimated 37.5 30.0            
X -4.5 7.5            

Remember that the moving range is just like the range for a subgroup of size 2. To calculate it we need to subtract the smaller X value from the greater:

mR = 7.5 - -4.5

Or because the two negatives combine to make a positive, we could say:

mR = 7.5 + 4.5

So what is the first moving range?