Question

If the annual income of the family in one of the regions of Kingdom of Saudi Arabia follows normal distribution, its Mean (   ) 100 thousand riyals, and its Variance is 1600

find the percentage of households whose income is over than 50 thousand riyal

Answer 1

Given

Over than 50:

P(X > 50) = ?

We know that the Standard Normal Variate is Z

%

e have to find out the Probability of the Shaded Area

Therefore the percentage of households whose income is over than 50 thousands is 89.44%

NOTE:

The value of P(-1.25 < Z < 0) = P(0 < Z < +1.25) has been extracted from the Standard Normal tabulatd value. In that Search the probability Value which is intersected between the Z values 1.2 and 0.05; we will get 0.3944