يلا نذاكر أحصاء سوآ ..

[محمد المحمدي 99]

the monthly income ,X, of a family in a given city is normally distributed with mean 3000 and standard deviation 500

THE PROBABILITY THAT A PERSON SELECTED AT RANDOM EARNS A MONTHLY INCOME BETWEEN 2500 and 3500

if a random sample of size 9 is selected at random , find the probability that the mean income of the sample is between 2500 and3500