# Knowing that the weight corresponding to the third quartile […] calculate the value of μ and the value of σ.

The weight in kg, of cubs in a year follow a standard deviation with a mean of μ and standard deviation σ.

(a) Knowing that the weight corresponding to the third quartile is 21,3kg and the weight corresponding to the first quartile is 17.1 kg, calculate the value of μ and the value of σ.

I know that I have to find two different equations in order to find the mean and the standard deviation, the only thing that i don't get is the quartile thing, if I try to find the normal continuous distribution in my calculator I need both the standard deviation (which equals 1) and the mean (which equals 0) then I need the lower and upper bound which I am not sure about, I am guessing it has something to do with the quartiles.

Any help is really appreciated :)

## 1 Answer

You have p=mu+0.67sigmafor the upper quartile andp=mu-0.67sigmafor the lower quartile. You are given values ofp. So just solve those two equations for mu and sigma(Please check values of 0.67 and -0.67 using z-table as I may remember those wrong)