Dawnbridge

TI-Nspire CX II field manual for IB Math

AI HL only · 40 of 45

40

Poisson distribution probabilities

AI HL

Use the Poisson cdf routine to find bounded probabilities P(a≤X≤b).

Goal

If ​X∼Po(4), find ​P(2≤X≤6).

1

From the Scratchpad calculator, press → 6: Statistics → 5: Distributions → K: Poisson Cdf.

2

The dialog takes the range directly: fill in ​λ=4, Lower Bound: 2, Upper Bound: 6, moving between fields with .

Scratchpad
RAD
Poisson Cdf
λ:4▶
Lower Bound:2▶
Upper Bound:6▶
OKCancel
3

Select OK and press . The poissCdf(4,2,6) command lands on the calculator page with its value.

Scratchpad
RAD
poissCdf(4,2,6)
0.797748
Result

​P(2≤X≤6)≈0.798.

Your turn

Work each one on your calculator, then check the answer.

  1. 1

    If ​X∼Po(5.5), find ​P(3≤X≤7).

  2. 2

    If ​X∼Po(3), find ​P(2≤X≤5).

  3. 3

    If ​X∼Po(7), find ​P(5≤X≤9).