TI-83 Instructions

Computing Binomial Probabilities

Binomial Probability of a Single Individual Value of X

1. Press 2nd DISTR. The DISTR menu titles appear. The menu title DISTR is highlighted.
2. Scroll down to select binompdf, the 10th item. (Or press 0 and skip the next step.)
3. Press ENTER. The phrase binompdf( appears in the display.
4. Enter the value of n (the number of trials).
5. Press comma.
6. Enter the value of p (the probability of success).
7. Press comma.
8. Enter the value of X (the number of successes for this event).
9. Press ) (close parenthesis).
10. Press ENTER. The binomial probability appears in the display.

Binomial Probability of Several Individual Values of X

Method 1

1. Store the individual values of X in list L1.
2. Follow the above instructions, except for step 8.
3. In Step 8, instead of entering the value of X, enter L1.
4. The result is a list of the individual binomial probabilities corresponding to the values of X.

Method 2

1. Follow the instructions to find the probability of one of the values of X.
2. Press 2nd ENTRY. The previous expression (not the answer) appears in the display. It is editable (but not edible).
3. Use the left and right arrow keys to move the cursor back to the value of X in the expression binompdf(n, p, x).
4. Press DEL. The old value is gone.
5. Press 2nd INS. The cursor changes shape. The new shape indicates that the calculator is in "insertion" mode.
6. Enter the new value of X.
7. Press ENTER. The binomial probability of the new value of X appears in the display.
8. Repeat this steps for each of the remaining values of X.

Cumulative Binomial Probabilities for Ranges of Values of X

Case 1: When the event is X ≤ a.

1. Press 2nd DISTR. The DISTR menu titles appear. The menu title DISTR is highlighted.
2. Scroll down to select the binomcdf, the 11th item. (Or press ALPHA A and skip the next step.)
3. Press ENTER.
4. Enter the value of n (the number of trials).
5. Press comma.
6. Enter the value of p (the probability of success).
7. Press comma.
8. Enter the value of a.
9. Press ) (close parenthesis).
10. Press ENTER. The binomial probability P(X ≤ a) appears in the display.

Case 2: When the event is X ≥ a.

1. Use the above instructions to compute P(X ≤ a − 1).
2. Subtract the result from 1. The new result is P(X ≤ a).

Case 3: When the event is a ≤ X ≤ b.

1. Use the above instructions to compute P(X ≤ b).
2. Use the above instructions to compute P(X ≤ a − 1).
3. Subtract P(X ≤ a − 1) from P(X≤ b). The result is P(a ≤ X ≤ b).