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Statistics and probability vocabulary words

This list is for students studying statistics or probability, including those preparing for an AP Statistics course. Use it to preview a unit on data analysis, review terms before a test on probability, or clarify the difference between related concepts like mean and median.

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Statistics and probability vocabulary words

30 words
WordMeaningIn a sentenceSave
meanverbTo 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.
mediannounThe 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.
modenounA 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.
rangenounThe 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.
variancenounA 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 deviationnounA 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.
probabilitynounThe 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.
outcomenounThe way a situation, action, or process finally turns out; a result.The outcome of the election surprised even the most experienced analysts.
sample spacenounIn probability, the set of all possible outcomes of a random experiment.For a single coin toss, the sample space consists of heads and tails.
eventnounA 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 eventnounIn 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 eventnounIn 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 exclusiveadjectiveDescribing 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 probabilitynounThe 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.
distributionnounThe action of distributing something, or the way something is spread or shared out.The company improved its distribution so stores received deliveries faster.
normal distributionnounA symmetric, bell-shaped probability distribution in which most values cluster around the mean.Test scores in the large class followed a roughly normal distribution.
correlationnounA 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.
causationnounThe 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.
regressionnounA 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.
hypothesisnounA proposed explanation that can be tested using observations or an investigation.Our hypothesis was that the seedlings would grow taller with more light.
null hypothesisnounIn 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 intervalnounA 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.
samplenounA 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.
populationnounThe 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.
biasnounAn 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 samplingnounA 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.
percentilenounA 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.
quartilenounIn 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.
outliernounA 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.
frequencynounThe 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.

Probability vocabulary

Probability describes how likely an event is to happen. A sample space lists all possible outcomes of an event, and two events are independent if one does not affect the other's outcome, while dependent events do affect each other. Mutually exclusive events cannot happen at the same time, and conditional probability measures the chance of an event occurring given that another event has already happened.

Frequently asked questions

What is the difference between mean, median, and mode?

The mean is the average of a data set, the median is the middle value when the data is ordered, and the mode is the value that appears most often.

What does 'standard deviation' measure?

Standard deviation measures how spread out data values are from the mean; a small standard deviation means values cluster closely together.