Hi
I have a task to complete, which is to calculate the mean and standard deviation of something. I have done this but am then asked to write a short explanation of my findings.
I know what the mean is about, and I thought
I knew what the standard deviation meant too - shows the variation
from the mean.
However, on a task I completed earlier the feedback I got said 'you
need to tell us that it is talking about the middle 66% of the data'
- that
has thrown me, I don't understand that. Can anyone help me get my
head round this???
Many thanks.
Rebecca
Hi Rebecca,
If you have a collection of data from a Normal Distribution then approximately 66% of the data should fall within one standard deviation of the mean. For exmple if the mean is 6 and the standard deviation is 1.2 then approximately 66% of the data is between
6 - 1.2 = 4.8
and
6+1.2 = 7.2
The same approximation is usually true if the data is approximately normally distributed and the data set is reasonably large. By "approximately normal" it is usually enough that a histogram of the data be approximately bell shaped and symmetric.
Penny