TI-Nspire CX II 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).
For P(X=5): press → 6: Statistics → 5: Distributions → A: Binomial Pdf. Enter Num Trials: 20, Prob Success: 0.3, X Value: 5, moving between fields with , then select OK and press . The binomPdf(20,0.3,5) command lands on the calculator page with its value.
For P(4≤X≤12): choose B: Binomial Cdf instead. Its dialog takes the range directly: Lower Bound: 4, Upper Bound: 12. Select OK and press ; binomCdf(20,0.3,4,12) lands on the calculator page with its value.
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).