Jump to content
Sign in to follow this  
Prasoon Bhargav

P Chart

Recommended Posts

Dear All,

Please see below a query posted by a past participant. Please feel free to respond to this query.


shantanu kumar


Hi Shantanu,

Hope you are doing well.

I was trying to understand p-charts. Consider a case where in the output is varying and defectives are identified. Data for the same is as follows. When I tried to plot a p-chart for the same in Minitab, the UCL line varies as shown because of varying output, but a value of UCL (0.05439) is highlighted; Similarly for LCL (0.00675). How is this figure arrived at?

Defective Volume

15 500

20 528

13 465

12 470

Warm Regards,

Krishnan S

Share this post

Link to post
Share on other sites

The UCL and the LCL shown are for the last data point (i,e, Defective = 12 and Volume = 470).


How do we arrive at these figures is as follows


1. First calculate pbar => find out individual proportions and then take the average of the same.

2. Control limits = pbar +- 3 times (square root(pbar(1-pbar)/N), N = sample size for the last sample (if you change the last data point, you UCL and LCL would change).


Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this