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How to easily create a control chart?

Step 1 : Collecting a data base

In reproductibility conditions, analyse a same batch of TITRIVIN and collect your results

Step 2 : exploiting the results

You are going to calculate :

  • the average

  • the reproductibility standard deviation of the laboratory srepro

Step 3 : defining the control chart parameters

You will define the different paramaters of your control chart to build the graphic.

The target

The target value Tv corresponds to the average.

The control limits

The upper control limit : Tv + 3 srepro
The lower control limit : Tv - 3 srepro

99.8% of the data normally distributed should be within these limits.
If the control value is outside the control limits, we talk about an “abnormal” result. That means there is a high probability that the analysis is wrong. So you have to take remedial actions.

The warning limits 

The upper warning limit : Tv + 2 srepro
The lower warning limit : Tv - 2 srepro

Provided that the results are normally distributed, about 95% of the results should be within these limits.

Step 4 : building the graphic

You can build your control chart on a sheet of paper or with a computer. 

Step 5 : analysing the chart

You will plot the new results of your internal quality control on this control chart.
According to their position, you can interpret your control results.

To know "how to analyse your control chart?" click here

Step 6 : validation or replacement of the control chart parameters

After collecting around thirty values, you have to assess the situation in order to validate or not the different parameters of your control chart.

If your control chart is ”abnormal“, you will calculate a new target value and / or standard deviation from all the results obtained from step 1.