This is my method of understanding as well.
Here’s an example of some chrono data from a 6gt.
34.6gr: Sd: 5.1 Es: 13
34.8gr: Sd: 6.7 Es: 15
35.9gr: Sd: 4.7 Es: 13
Well, if we just looked at ES, we’d think these are all very close. One may even think 34.6 is same because it had the same ES of 13 as the 35.9.
However, statistically we know that 99.7% of shots will be within 3 standard deviations each way.
That means 6x your SD.
Now, that means:
34.6: ES: 30.6
34.8: ES: 40.2
35.0: ES: 28.2
All of a sudden that 15es in the middle that looked very close to the others is much further apart.