Casio fx-CG50 field manual for IB Math
Normal distribution probabilities
Use the normal CDF command to calculate probabilities P(a<X<b) from a normal distribution.
If X∼N(60,52), find P(X<68).
From the MAIN MENU, open Statistics. If you're already inside another app, press first to get back to MAIN MENU.
Press (DIST), then (NORM), then (Ncd) to open the normal cumulative distribution wizard.
Press (Var) to switch Data from List to Variable, so you can type the bounds directly.
Fill in the form, pressing after each value: for Lower type 1 10 (a very large negative number standing in for −∞), then Upper 68, σ=5, and μ=60. The calculator asks for σ before μ.
Move down to Execute and press .
P(X<68)≈0.945.
Your turn
Work each one on your calculator, then check the answer.
- 1
If X∼N(100,152), find P(X<120).
- 2
If X∼N(50,82), find P(X>60).
- 3
If X∼N(3.2,0.42), find P(3<X<3.9).