Question

Historically, the average diameter of the holes drilled has been 0.25 cm and the average range has been 0.10 cm. Samples of size 4 will be collected. For the R-chart, what is the value of upper control limit

Answer 1

Solution :

Given the average range of the holes drilled = 0.10 cm

The average diameter of the holes drilled = 0.25 cm

The sample size = 4

For the sample size of 4, the factor for control limit for the range ($D_4$) = 2.28  (From the table of constants for X-bar and R-chart)

The upper control limit for the R-chart = R-bar x $D_4$

                                                                = 0.10 x 2.28

                                                                = 0.228

Therefore, the answer is greater than 0.202 but less than or equal to 0.302