Finding the expected value and standard deviation of a ...

[Pages:1]Finding the expected value and standard deviation of a random variable

using a TI-84 calculator

In L1, enter the values for the random variable X. In L2, enter the frequency for each value.

Multiply L1 and L3 and store the products in L4.

The sum of L4 will be the expected value for the random variable. Calculate the sum and store it as B.

Find the sum of L2. Find the function sum( in the catalog by pressing CATALOG, then choosing the letter T (above the 4 key). Cursor up twice until you see the sum function. Store this number as A on your calculator.

To calculate the variance, you need to find the squared deviations from the expected values and multiply by the probabilities. Store these values in L5.

The sum of L5 is the variance.

Next, divide each number in L2 by A, and store the resulting probabilities in L3.

The square root of the variance is the standard deviation of the random variable.

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