TI-84 Plus CE field manual for IB Math
Inverse normal
Use the inverse-normal routine to find the value k with a given cumulative probability P(X<k).
If X∼N(60,52), find k such that P(X<k)=0.9.
Verify STAT WIZARDS is set to ON: press and check the row near the bottom of the screen. With it off, the DISTR menu items paste a bare command instead of opening the input wizard, so there's no Tail option to set. Press to return to the home screen.
Open the distribution menu with , then choose 3: invNorm(.
Fill in the wizard: area: 0.9 (the probability to the left of k), μ=60, σ=5, and Tail: LEFT.
Choose Paste, then press to evaluate the pasted command.
k≈66.4.
Your turn
Work each one on your calculator, then check the answer.
- 1
If X∼N(100,152), find k such that P(X<k)=0.95.
- 2
If X∼N(24,32), find k such that P(X<k)=0.10.
- 3
If X∼N(70,62), find k such that P(X<k)=0.25.