Question

A software developer has measured the number of defects per 1,000 lines of code in software modules being developed by the company. Construct the appropriate chart(s) for these data using 3 sigma control limits. Is the process in control? Why or why not?

Sample	Number of defects per 1,000 lines of code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15	5 10 11 2 6 8 12 2 7 3 6 10 9 1 4

Answer 1

This question will be solved using P value control charts. First of all we need to calculate mean, Standard Deviation, UCL (Upper Control Limit) and LCL (Lower Control Limit) for the given data.

Following formulas will be used to for calculation:

We can use following formulas in excel to calculate the same:

Please note: The minimum value of LCL is 0. It cannot be negative because number of defects in a line of code cannot be negative. In the image below i have shown the actual outcome. However the value of LCL will be 0

Using the above formulas we wil get the following results:

This data can be represented inthe form of graph as follows:

From this graph we can see that all the observations are within the control limits and thus we can say that the process is under control.