# TI 83 Central Limit Theorem in Easy Steps

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## TI 83 Central Limit Theorem: Overview

The TI 83 calculator is probably the most widely used calculator in statistics, because of its array of built-in statistical functions.

The Central Limit Theorem (CLT) is a way to show characteristics for the “sampling distribution of the means,” taken from a “parent population” which is created from the means of an infinite number of random population samples of size (N). It tells us that the distribution of means will be approximately normally distributed as N gets larger. In addition, the mean of the sampling distribution of the means and the standard deviation of the population means will equal the mean and standard deviation of the parent population.

The TI 83 calculator has a built in function that can help you calculate probabilities of central theorem word problems, which usually contain the phrase “assume the distribution is normal” (or a variation of that phrase).

The function, normalcdf, requires you to enter a lower bound, upper bound, mean, and standard deviation.

## TI 83 Central Limit Theorem: Steps

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: 2nd VARS 2.

Step 2: Enter your variables (lower bound, upper bound, mean, and standard deviation). Separate each variable by a comma: 9,9.5, 10,(1.25/√15)).

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

Tip:If you have a question that asks for “greater than” or “less than” a certain number, enter 999999999 for the lower or upper bound. For example, if you wanted to know the probability of greater than 8 pounds you would enter:
NORMALCDF(8,999999999,10,1./√(15))
Less than 8 pounds you would enter:
NORMALCDF(999999999,8,10,1./√(15))

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

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TI 83 Central Limit Theorem in Easy Steps was last modified: September 7th, 2015 by

# 3 thoughts on “TI 83 Central Limit Theorem in Easy Steps”

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 ???