Empirical Rule - Problem?
(gas prices) if the mean is $1.47 and the standard deviation is $0.08
how can I find what percentage was sold between $1.39 and $1.55? Can you talk me through this? I'm not sure how the work is done.
Thanks in advance!
Update:Thank you, you've helped me a lot!
1 more question...
If instead of 1.55, it were 1.63, how would I do it?
1.63-1.47/0.08?
Comments
According to the empirical rule
Mean +/- 1 SD covers 68% of the items
Mean +/- 2 SD covers 95% of the items
Mean +/- 3 SD covers 99.7% of the items
Thus the empirical rule is stated as 68-95-99.7
z = (X-Mu)/SD
z1 = (1.39-1.47)/0.08 = - 1
z2 = (1.55-1.47)/0.08 = + 1
Therefore the required percentage = 68%