normalcdf and invNorm calculator, with TI-84 steps
Get the area or the critical value, see it shaded, and press the same keys on your TI-84. Also does tcdf and invT.
Area
0.6827
68.3% of the curve is between −1 and 1.
On a TI-84 Plus
- Open the command2ndVARS2
- lower:(−)1ENTER
- upper:1ENTER
- μ:0ENTER
- σ:1ENTER
- Paste, then answerENTERENTER
Screennormalcdf(-1,1,0,1)
Stat Wizards off? Type the line above, then ENTER. Use (−) for a minus sign.
Which command do I need?
| The probability of a value below, above or between numbers on a normal curve | normalcdf |
|---|---|
| The value that cuts off a given area, such as the 90th percentile | invNorm |
| z* for a confidence interval | invNorm, with the middle area |
| A p-value from a t statistic | tcdf |
| t* for a confidence interval | invT, with the middle area |
Areas to the left
invNorm and invT always take the area to the left. For the top 10%, the area to the left is 0.90. For 95% confidence, the middle 0.95 leaves 0.025 in each tail, so the area to the left of z* or t* is 0.975.
For a p-value from a two-sided test, find the area in one tail with normalcdf or tcdf, then double it.
Find your weakest unit
A free 32-minute diagnostic across all five units. No account. You get your score in each unit and a short lesson on the one to fix first.
Questions people ask
How do you do normalcdf on a TI-84?
Press 2nd, then VARS to open DISTR, then 2 for normalcdf(. Enter the lower bound, upper bound, mean and standard deviation, pressing ENTER after each, then ENTER on Paste and ENTER again. With no lower bound use -1E99, and with no upper bound use 1E99.
What is the difference between normalcdf and invNorm?
normalcdf turns values into an area, which is a probability. invNorm goes the other way: it takes the area to the left and gives the value.
How do you find t* on a TI-84?
Use invT with the area to the left of t*. For 95% confidence that area is 0.975, so type invT(0.975, df). With 19 degrees of freedom, t* is 2.093.
What does 1E99 mean on a TI-84?
1 × 10⁹⁹, a number so large the calculator treats it as infinity. Type it with 1, then 2nd and the comma key (EE), then 9 and 9. Use the (−) key, not the minus key, for -1E99.
Can you use a calculator on the AP Statistics exam?
Yes. College Board expects a graphing calculator with statistics functions on both sections, the TI-84 Plus family is on its approved list, and Bluebook has a built-in Desmos graphing calculator.