mean verb To intend to express, convey, or refer to a particular thing or idea. I'm not sure what he meant by that strange comment at dinner. + median noun The middle value in a set of numbers arranged in order, or a line dividing something into two equal parts. The median income in the town was lower than the national average. + mode noun A particular way, method, or manner in which something is done or occurs. The printer has a draft mode that saves ink but lowers print quality. + range noun The full extent of variation between an upper and a lower limit on a particular scale. The store carries a wide range of sizes to fit almost any customer. + variance noun A statistical measure of how spread out a set of values is from their average. A low variance in test scores showed that most students performed similarly. + standard deviation noun A statistical measure of how spread out a set of values is from the average. A low standard deviation means most test scores clustered close to the class average. + probability noun The likelihood that a particular event will occur, often expressed as a number or percentage. The probability of rain tomorrow is fairly high according to the forecast. + outcome noun The way a situation, action, or process finally turns out; a result. The outcome of the election surprised even the most experienced analysts. + sample space noun In probability, the set of all possible outcomes of a random experiment. For a single coin toss, the sample space consists of heads and tails. + event noun A thing that happens, especially one that is significant, planned, or notable. The wedding was the biggest event our small town had seen in years. + independent event noun In probability, an event whose outcome does not affect or depend on the outcome of another event. Flipping a coin twice produces independent events because each flip has no effect on the other. + dependent event noun In probability, an event whose outcome or likelihood is affected by a previous event. Drawing a second card without replacement is a dependent event in probability. + mutually exclusive adjective Describing two events, options, or categories that cannot both be true or exist at the same time. Being a full-time student and a full-time employee are nearly mutually exclusive here. + conditional probability noun The likelihood of an event occurring given that another related event has already happened. The conditional probability of drawing a king, given the card is a face card, is one third. + distribution noun The action of distributing something, or the way something is spread or shared out. The company improved its distribution so stores received deliveries faster. + normal distribution noun A symmetric, bell-shaped probability distribution in which most values cluster around the mean. Test scores in the large class followed a roughly normal distribution. + correlation noun A mutual relationship or connection between two or more things, especially one where they tend to change together. Scientists found a strong correlation between exercise and improved sleep quality. + causation noun The relationship between a cause and its effect, where one event directly brings about another. Scientists were careful to distinguish correlation from true causation in their study. + regression noun A return to an earlier, less developed, or worse state or way of behaving. After the accident, the patient showed a regression in his ability to speak clearly. + hypothesis noun A proposed explanation that can be tested using observations or an investigation. Our hypothesis was that the seedlings would grow taller with more light. + null hypothesis noun In statistics, the assumption that there is no effect or difference, tested against the possibility of a real one. The researchers could not reject the null hypothesis, so the drug showed no clear benefit. + confidence interval noun A range of values, calculated from sample data, likely to contain the true population value. The poll reported a 95 percent confidence interval of plus or minus three points. + sample noun A small part or quantity of something intended to show what the whole is like. The nurse took a blood sample to test for signs of infection. + population noun The total number of people, or of a particular species, living in a given area. The population of the small town has grown by nearly a third in ten years. + bias noun An unfair tendency to favor or oppose a particular person, group, or idea, often without a fair basis. The study was designed to reduce bias by keeping researchers unaware of who received the treatment. + random sampling noun A method of selecting a sample in which every member of the population has an equal chance of being chosen. The researchers used random sampling to select five hundred voters from the national registry. + percentile noun A value on a scale showing the percentage of a data set that falls below it. Scoring in the 90th percentile means the student did better than 90 percent of test takers. + quartile noun In statistics, one of three values that divide a set of ordered data into four equal parts. Students scoring in the top quartile earned scholarships to the university's honors program. + outlier noun A person, thing, or data point that differs markedly from the rest of a group or set. One student's test score was such an outlier that the teacher rechecked it for errors. + frequency noun The rate at which something happens or is repeated over a particular period of time. Doctors track the frequency of her headaches to identify possible triggers. +