Probability & Distributions Tools

Probability Calculator opens this category because most probability problems collapse into three shapes: the chance of exactly k successes in n independent trials, the likelihood of an event over a fixed interval, and whether a continuous outcome falls above or below a threshold. Basic Probability handles the first shape directly — enter any event count and sample space size and it computes the probability, its complement, the odds ratio, and the log-odds in one panel. Expected value and variance follow automatically so a visitor asking "what is the average number of times this happens" does not need a second tool.

Normal Distribution Calculator sits here alongside it: enter a mean, a standard deviation, and a value, and it returns P(X < x), P(X > x) and P(a < X < b) using the error function computed to six significant figures. The Z-score is shown explicitly rather than buried, because knowing the score is usually as useful as knowing the probability it corresponds to.