## Solving Central Limit Theorem Word Problems on the TI-83 Graphing Calculator

The TI 83 calculator has a built in function that can help you calculate probabilities of central theorem word problems. The function, normalcdf, requires you to enter a lower bound, upper bound, mean, and standard deviation.

Sample problem: A fertilizer company manufactures organic fertilizer in 10 pound bags with a standard deviation of 1.25 pounds per bag. What is the probability that a random sample of 15 bags will have a mean between 9 and 9.5 pounds?

Step 1: , .

Step 2: Enter your variables (lower bound, upper bound, mean, and standard deviation): .

Step 3: Press . This returns the probability of .05969, or .05969%.

Tip: Sampling distributions require that the standard deviation of the mean is σ / √(n), so make sure you enter that as the standard deviation.

## 3 thoughts on “Solving Central Limit Theorem Word Problems on the TI-83 Graphing Calculator”

1. Dan Martin

Why is it when I enter the numbers into my Ti-83 exactly as shown, I get 4.8236763E-7

I have used this same calculation for nomalcdf(60,64,62.4, (3.1/sqrt12))= .9594453925
which according to my study materials is correct.

I have no idea how your calculation comes up with .159, is this actually incorrect or a typo ???