The average value cannot measure stability.
Difference calculation method,
For example, group A, choose a good reference number, such as 900,
Subtract 900 from each number to get new data.
-96,84,89,-83, 19,-60, 12, 10 1
The variance is
(96? +84? +89? +83? + 19? +60? + 12? + 10 1? )÷8-8.25?
This calculation should be easier.