Find the indicated percentile Assume that the random variabl

Find the indicated percentile. Assume that the random variable X is normally distributed with mean mu = 60 and standard deviation sigma = 9. Find the 55th percentile for X.

Solution

given mean =60; standard deviation =9 ;

55 the percentiale is P(X<=X\') = 0.55

P(Z<= (X\'-60)/9)=0.55;

From normal probability tables P(Z<=0.12566) = 0.55

so  (X\'-60)/9=0.12566

X\' = (0.12566*9)+60 = 61.131