Dawnbridge

TI-Nspire CX II field manual for IB Math

Everyone · 27 of 45

27

Binomial probabilities

All courses

Use the binomial pdf and cdf routines to find P(X=k) and range probabilities P(a≤X≤b).

Goal

If ​X∼B(20, 0.3), find ​P(X=5)​ and ​P(4≤X≤12).

1

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.

Scratchpad
RAD
binomPdf(20,0.3,5)
0.178863
2

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.

Scratchpad
RAD
binomCdf(20,0.3,4,12)
0.891634
Result

​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. 1

    If ​X∼B(15,0.4), find ​P(X=6)​ and ​P(5≤X≤9).

  2. 2

    If ​X∼B(25,0.2), find ​P(X=4)​ and ​P(3≤X≤8).

  3. 3

    If ​X∼B(30,0.6), find ​P(X=18)​ and ​P(15≤X≤22).