A simple and easy-to-understand explanation of Shewhart control charts for individual measurements, designed for 11-year-old students to grasp the basic concepts of monitoring processes with charts.
Imagine you are checking how well something is working, like how long it takes your homework to finish or how many candies you get each day. A Shewhart control chart helps us keep an eye on changes by plotting numbers in order, so we can see if everything is normal or if something strange is happening.
First, you measure whatever you want to watch — for example, the time it takes you to finish a math problem every day. These are called individual measurements because you take one at a time.
Next, you put each measurement on a graph in the order you took them. On the bottom, you put the day (like Day 1, Day 2, etc.), and on the side, you put how long it took.
Now, find the average (mean) time it took you to finish the problems. This is like finding the middle value of all your measurements.
We draw lines above and below the average line, called control limits. These lines show the usual range of variation. If your times stay inside these lines, your process is working normally. If points go outside, something might have changed.
This chart helps you see if your process is steady or if there are unusual changes you need to investigate. It's used a lot in factories and other places to make sure everything works well.
By using this chart, you can keep track of your work or anything else you want to measure in a simple way!