# User:Kevin Tan/Probability Distribution

From WikiEducator

Example : If *N*(42, 9) , evaluate

(i) *P(X < 44)*

(ii)*P(40 < X < 45)*

Solution: To use the standardised normal distribution table, you’ve to understand :

1. that 42 is the mean and 9 is the variance.

2. Then, need to convert P(3.X) to P(Z) by using the formula P(Z< [math]\frac{x-\mu}{\sigma})[/math]

4. The area below the curve is the probability, corresponding to the value of ‘z’ and the value from the table is just for the shaded region. 5. The graph is a symmetrical graph and we are reading the area of HALF the graph only. 6. The total area under the graph is 1 (ONE) and area of 0.5 on each side.

The worked example below will hopefully make it clear,…..