Use of TI-83 Calculator to Compute
Poisson Probability Distribution Values

Example (TI-83): Find the probability that 3 successes will occur if the average number of successes is 3/4. That is, find P(x = 3).
Press 2^nd VARS [DISTR]. Scroll down to C:poissonpdf( Press ENTER.
Enter 3/4,3) and press ENTER to get the answer .03321. The syntax is poissonpdf(mean, x-value).
Example (TI-83): Find the probability that 3 or less successes will occur if the average number of successes is 3/4. That is, find P(x ≤ 3).
Press 2^nd VARS [DISTR]. Scroll down to D:poissoncdf( Press ENTER.
Enter 3/4,3) and press ENTER to get the answer .9927. The syntax is poissioncdf(mean, largest x-value).
Example (TI-83): Find the probability that at least 3 successes will occur if the average number of successes is 3/4. That is, find P(x ≥ 3). Use the complement rule to find P(x ≥ 3) = 1 – P(x ≤ 2).
Press 1 – and 2^nd VARS [DISTR]. Scroll down to D:poissoncdf( Press ENTER.
Enter 3/4,2) and press ENTER to get the answer .0405. The syntax is 1 – poissoncdf(mean, largest x-value).