Thread: On the p chart

i confused in this subject guys!!

On the p chart, what process variable is plotted?
1-fraction of defective units in the sample
2- sample means
3-number of defects in a given unit of process output
4- range of the process variable observed in a sample

thank you for answering

Originally Posted by selimcan

i confused in this subject guys!!

On the p chart, what process variable is plotted?
1-fraction of defective units in the sample
2- sample means
3-number of defects in a given unit of process output
4- range of the process variable observed in a sample

thank you for answering

For P-Chart you plot the criteria of interest separately.

You plot the fraction of defects , Center Line (CL), Upper Control Limit (UCL), and the maximum of the Low Control Limit (LCL). This is more engineering than math. It's quite straight forward. You just need to input all your data on excel in each column. The first column list the trials in sequence; the second, the number of defects in each trail; the third is the number of sample in each trail; the fourth is obtained by dividing column 2 by column 3.

You sum column 2 and get the total defects; next, sum column 3 total possible in all the trails (ie, total samples in all the trails. You take sum from column 2 divide it by sum from column 3. That give you the Average proportion.

Use 5th column for UCL; 6th for CL, and 7th for Maximum of LCL.

Plot them separately and label each P-Chart according to their category. Then you are home free.