Calculating Mean and Variance of a Normal Distribution

jinx007
Messages
60
Reaction score
0
Please try this question and see whether you got my answer...i am having some doubt

The random variable X is normally distributed with mean V and variance C^2. It is known that P(x>102)=0.42 and P(x<97)=0.25

calculate V(mean) and variance c^2

i got mean 100.8 and variance(-5.7)^2
 
Physics news on Phys.org
You need to show some work, but one comment: if you say the variance is (-5.7)^2, you are implicitly saying the standard deviation is -5.7, which is impossible.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top