Question

You want to determine the lower control line for a p-chart for quality control purposes. You take several samples of a size of 50 items in your production process. From the samples you determine the fraction defective is 0.006 and the standard deviation is 0.001. If the desired confidence level is 99.7 percent, which of the following is the resulting LCL value for the line?

A. 0.001
B. 0.002
C. 0.003
D. 0.004
E. None of these

Answer 1

Answer: C. 0.003

Explanation:

The LCl value of the line for 99.7% confidence level is given by :-

`\mu-3\sigma ,` where
`\mu` is population mean and
`\sigma` is standard deviation.

As per given we have,

`\mu=0.006\\\\\sigma=0.001`

Then, the LCL value for the line is given by :-

`0.006-3(0.001)=0.003`

Hence, the resulting LCL value for the line is 0.003.