Distributions & Models Vocabulary

a symmetric bell-shaped probability distribution

“Heights in a population follow approximately a normal distribution.”

Origin: From normal (Latin normalis `made according to a rule`) + distribution

relating to experiments with two possible outcomes

“The number of successes in n trials follows a binomial distribution.”

Origin: Latin bi- `two` + nomen `name, term`

a distribution modeling rare events over fixed intervals

“The number of calls per hour follows a Poisson distribution.”

Origin: Named after Siméon Denis Poisson, French mathematician (1781-1840)

a distribution modeling time between events in a Poisson process

“Wait times often follow an exponential distribution.”

Origin: Latin exponere `to put forth`, from ex- + ponere `to place`

a distribution where all outcomes are equally likely

“A fair die has a discrete uniform distribution.”

Origin: Latin uniformis `having one form`, from unus `one` + forma `form`

a measure of asymmetry in a probability distribution

“Income distributions typically show positive skewness.”

Origin: From skew (Old Norse skeifr `oblique`) + -ness

a measure of the 'tailedness' of a probability distribution

“High kurtosis indicates more extreme outliers.”

Origin: Greek kyrtos `curved, arched` + -osis

involving two or more random variables

“Multivariate analysis considers multiple variables simultaneously.”

Origin: Latin multi- `many` + variare `to change`

the value below which a given percentage of observations fall

“Scoring in the 95th percentile means outperforming 95% of test-takers.”

Origin: Latin per centum `by the hundred` + -ile

an observation that lies far from other values

“The billionaire's income is an outlier in the dataset.”

Origin: From out + lie, one who lies outside