Association: The trend in a graph that shows the effect on one measure by a second measure.

Biased sampling: A sample that overrepresents or underrepresents part of the population.

Bar graph: A graph of data with parallel bars used for comparing information on categories where each bar represents a category and the height or length of the bar represents the number of events in that category.

Bivariate data: Data or events described using two variables.

Box-and-whisker plot: A diagram that shows pictorially the median and measures of spread (upper and lower interquartile ranges and the range) for one set of data.

Broken-scale symbol: Is used at the end of the axis to indicate that the graph does not begin at the origin (0,0).

Causation: The relationship between two variables where a change in one variable affects the outcome of the other variable.

Categorical data: Data that can be classified by type; e.g., color, types of dogs. These types of data are typically represented using bar chart, pie charts or pictographs.

Census: When every member of the population has data collected from them.

Clusters and gaps: Numbers that tend to crowd around a particular point in a set of values. The spaces between the clusters are called gaps.

Combination: A selection of a group of items or events from a set without regard to order; e.g., the number of three-piece outfits from the set of clothes in the closet.

Complementary events: Two or more mutually exclusive events that together cover all possible outcomes. The sum of the probabilities of complementary events is one.

Compound events: Combining two or more independent events or outcomes and considering it as one single event or outcome.

Conditional probability: The probability of an event occurring given that another event has already occurred. For example: What is the probability that the total of two dice will be greater than eight given that the first die is a six?

Continuous data: Data that can be assigned an infinite number of values between whole numbers, the assigned values are approximated; e.g., the size of the apples on an apple tree is continuous data. See discrete data for a counterexample.

Convenience data: Data that has been gathered with the group at hand.

Coordinate plane: A plane determined by the intersection of two perpendicular number lines in which any point can be located.

Coordinates: An ordered pair of numbers used to show a position on a graph. The first number (X) gives the place left or right and the second number (Y) gives the place up or down (X,Y).

Correlation: The relation between two sets of data, a positive or direct correlation exists when both sets vary in the same direction (both sets decrease); a negative or inverse correlation exists when one set of data increases as the other decreases.

Correlation coefficient: A measure of the correlation between two variables or sets of data. The value of the correlation coefficient, r, is always -1 to 1, where 1 is perfect positive correlation, 0 is no correlation, and -1 is perfect negative correlation.

Cumulative frequency: A running total of frequencies.

Datum: A single piece of data. The singular form of data.

Dependent events: A statement or probability for one event affects a statement or probability for another event.

Descriptive statistics: Gathered and described data using probability, statistical methods and concepts like graphs and measures of center.

Discrete data: Data that can be counted; e.g., the number of people in a town is discrete (there is no such thing as a fractional person). See continuous data for a counterexample.

Disjoint events: Two events that have no outcomes in common.

Dispersion: How data is spread out around some central point.

Distribution: A graph or table showing how many pieces of data there are in each class, or of each type.

Equation: A statement that shows two mathematical expressions that are equal to each other.

Event: An outcome of a probability experiment.

Experiment: The collecting of data through a planned investigation.

Experimental probability: The probability based on a series of trials. The experimental probability, P, can be found using the following equation:

P(event) =	# of trials w/favorable outcomes
	number of trials in experiment

 

Experimental results: The outcome as a result of a probability experiment or test. These outcomes are sometimes called actual results.

Extrapolation: A term used in interpreting scatter plots that predicts the location of points extending beyond the data displayed.

Frequency: The number of times an occurrence takes place as expressed in a count. The count is the frequency.

Frequency distribution: A collection of data that represents the number of times a set of numbers, items or events has occurred.

Frequency table: A table that shows how often each item, number or range of numbers occurs in a set of data.

Geometric probability (area models): The probability that a random point is located in a particular part subregion or larger region.

Glyph: A picture that represents data.

Histogram: Shows how measurements spread out across a real number line, marked off in equal intervals. The height of the bar represents the frequencies of measurements contained in that interval.

Independent event: Two events in which the outcome of the first event does not affect the outcome of the second event.

Intercepts: The value of y on the coordinate plane where x = 0, called the y-intercept. The value of x on the coordinate plane where y = 0, called the x-intercept.

Interpolation: A term used in interpreting scatter plots that predicts the location of points that would lie between those points of the data already displayed.

Interquartile range: The difference between the upper quartile and the lower quartile.

Interval: The distance on a real number scale between two consecutive tick marks or the space between the two points.

Line of best fit: A line drawn in the midst of the points on a scatter plot in an attempt to estimate the mathematical relationship between the variables used to generate the plot.

Line plot: A graph that indicates the location of data points along a segment of the real number line.

Linear equation: An equation whose graph on a coordinate grid is a straight line.

Lower extreme: The lowest value in a set of data.

Lower quartile: When data is ordered from smallest to largest and divided into four quarters, the values that are in the lower quarter of the data.

Matrix: A rectangular array of numbers or symbols.

Measurement data (quantitative): Has a numerical value and could be placed on a number line.

Measures of center: Numbers that provide information about cluster and average of a collection of data. They include the mean, mode and median.

Measures of spread or variability: A term used to refer to how much numbers are spread, varied or dispersed in a set of data. They include range, quartile and interquartile range.

Mean: The sum of a set of numbers divided by the number of elements in the set.

Median: The middle number or item in a set of numbers or objects arranged from least to greatest, or the mean of the two middle numbers when the set has two middle numbers.

Mode: The number or object that appears most frequently in a set of numbers or objects.

Mutually exclusive events: Two events that cannot occur at the same time.

Negative association: A pattern in the shape of the data that shows when one measurement grows larger, the second measure grows smaller. A negative association will be slanted downward from left to right.

Odds of an event: The ratio of favorable outcomes to unfavorable outcomes.

Ordered pairs: A pair of numbers that gives the coordinates of a point on a grid in this order (horizontal coordinate, vertical coordinate). Also called paired data or paired coordinates.

Origin: The point on a coordinate plane where the x-axis and the y-axis meet and have the ordered pair (0,0).

Outcome: Any possible result of an activity or experiment.

Outlier: A data point in a sample widely separated from the main cluster of points in the sample.

Parallel box plots: Two or more box plots using the same number line to allow comparison of the data.

Population: A whole set of individuals, items or data from which a sample is drawn.

Permutations: Possible orders or arrangements of a set of events or items.

Positive association: The pattern in the shape of data that shows when one number gets larger, the second also gets larger. It will be slanted upward from the left to right.

Probability: The chance of an event occurring. The probability of an event is equal to the number of favorable outcomes divided by the number of possible outcomes.

Pictograph: The use of a repeat picture in a bar graph form, to represent data.

Quadrants: The four separate sections formed by the two axes of a coordinate system. These are identified as the first, second, third and fourth quadrants.

Qualitative data: Data that can be assigned qualities or categories. They are nonnumerical data.

Quantitative data: Data that are numerical. The data can be discrete or continuous.

Quartile: In conjunction with the median, the quartiles divide the set of data into four groups of equal size.

Random sample: A sample in which every event has an equal chance of selection and each event is chosen by a random process.

Random variable: A variable that takes any of a range of values that cannot be predicted with certainty.

Range: The difference between the greatest and the least numbers in a set of data.

Rank: Placing a numerical order according to scale or value.

Relative frequency: The number of times an event occurs divided by the total number of trials.

Sample: A set of data taken from a larger set used to create or test theories about the data as a whole.

Sample space: A list of all possible outcomes of an activity.

Sampling method: The process used to collect data; see random sample.

Scale: The regular intervals of the number line that are chosen to represent the full range of data on a graph.

Scatter plot: A graph with one point for each item being measured. The coordinates of a point represent the measure of two attributes of each item.

Simple event: A subset of the sample space that contains only one outcome that cannot be broken down into a simpler, more basic outcome.

Simulation: The study of probability by collecting mathematically appropriate data that models an actual event.

Slope of 1: A line that contains points where the abscissa (x value) and the ordinate (Y value) are equal. (The rise equals the run.)

Stem-and-leaf plot: A frequency diagram that displays the actual data together with its frequency, by using a part of the value of each piece of data to fix the class or group (the stem), while the remainder of the value is actually listed (the leaves).

Survey: A question or set of questions answered by a population of people.

Symbolic form: A representation of something using numbers and symbols.

Target population: The set from which a sample will be selected.

Theoretical probability: Identifying, using mathematical expectations, the number of ways an event could happen compared to all the events that could happen.

Theoretical results: The expected results given the theoretical probability of an event.

Tree diagram: A graphic representation that resembles the branching out of a tree. It is used to illustrate outcomes of an event.

Trend: An emerging pattern in the shape of a data display that can be seen on a scatter plot.

Univariate data: Having one variable.

Upper extreme: The largest value in a set of data; the maximum.

Upper quartile: When data is ordered from smallest to largest and divided into four quarters, the values that are in the upper quarter of the data.

Variable: A changing quantity, usually a letter in an algebraic equation or expression, that might have one of a range of possible values.

Variance: A measure of the dispersion of the distribution of a random variable.

Variants: A quantity whose value may change or vary.

X-axis: The horizontal axis on a coordinate grid.

Y-axis: The vertical axis on a coordinate grid.

Definitions are from the Ohio State Content Standards for Mathematics and Exploring Statistics in the Elementary Grades by Bereska, Boster, Bolster and Scheaffer. (Dale Seymour Publications)