Normal CDF Calculator Cumulative Distribution Function states that the probability of the real-valued random variable X, will always take a value less than or equal to X. The upper bound is the right most number on the normal curve’s horizontal axis. This tutorial explains how to use the following functions on a TI-84 calculator to find normal distribution probabilities: normalpdf(x, μ, σ) returns the probability associated with the normal pdf where: x = individual value; μ = population mean 31. powered by. The normal distribution calculator works just like the TI 83/TI 84 calculator normalCDF function. Quick Normal CDF Calculator This calculator finds the area under the normal distribution curve for a specified upper and lower bound. Use the CDF to determine the probability that a random observation that is taken from the population will be less than or equal to a certain value. Upper bound: * Enter a number or 1E99 for positive infinity. 8. 9 6. It takes 4 inputs: lower bound, upper bound, mean, and standard deviation. It is also referred as cumulative density function or shortly, CDF. 3. s = 1. Then, use that area to answer probability questions. The lower bound is the left-most number on the normal curve’s horizontal axis. P(a