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 ([tex]D_4[/tex]) = 2.28 (From the table of constants for X-bar and R-chart)
The upper control limit for the R-chart = R-bar x [tex]D_4[/tex]
= 0.10 x 2.28
= 0.228
Therefore, the answer is greater than 0.202 but less than or equal to 0.302
