Casio fx-CG50 field manual for IB Math
Binomial probabilities
Use the binomial pdf and cdf routines to find P(X=k) and range probabilities P(a≤X≤b).
If X∼B(20, 0.3), find P(X=5) and P(4≤X≤12).
From the MAIN MENU, open Statistics, then press (DIST) and (BINOMIAL).
For P(X=5): choose Bpd, press (Var) if Data shows List, and fill in x = 5, Numtrial = 20, p = 0.3. Move down to Execute and press . The calculator prints the probability p on the results screen.
For P(4≤X≤12): back in the BINOMIAL menu choose Bcd: its wizard takes the range directly. Fill in Lower = 4, Upper = 12, Numtrial = 20, p = 0.3, then move to Execute and press to print p.
P(X=5)≈0.179 and P(4≤X≤12)≈0.892.
Your turn
Work each one on your calculator, then check the answer.
- 1
If X∼B(15,0.4), find P(X=6) and P(5≤X≤9).
- 2
If X∼B(25,0.2), find P(X=4) and P(3≤X≤8).
- 3
If X∼B(30,0.6), find P(X=18) and P(15≤X≤22).