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.
