T Distribution

Also called “Student’s Distribution” because the man credited for devising it published his work under the pseudonym “Student.” We’d have picked something cooler like “Shmoopy Shmooperton.”

The t-distribution is continuous probability distribution that arises when we are sampling for the purpose of estimating some unknown population value in situations where either the sample size is too small or, much more likely, when we don’t know the population’s standard deviation.

The t-distribution is a relatively close cousin of the standard Normal distribution but differs in a key way. While the standard Normal curve which is always the same shape regardless of how many data points we have in our sample, the t-distribution changes shape based on the number of degrees of freedom which is always one less than the number of data points. For large sample sizes, the t-distribution and the standard Normal curve are nearly identical.