Statistics

Box-And-Whisker Plot/Boxplot

A boxplot splits the data set into quartiles, where the middle 50% of the data forms the box and the lower 25% and upper 25% form the whiskers. Boxplots are used with larger sets of data. You can easily identify the median, the shape or skewness of the graph, and the range on a boxplot.

Pie Chart

A graph in which a circle is divided into sectors that each represent a proportion of the whole. Pie charts are helpful when displaying the relative distribution of categories.

Dot Plot

A graph that uses dots to show the frequency counts of a group of data. Dot plots are used for small sets of quantitative data. You can easily identify the mode, the shape or skew of the graph, and potential outliers on a dot plot.

Normal Distribution

A graph with a bell-shaped curve, where the graph is symmetric and has no skew.

Bar Graph

A visual representation of data which compares values in different categories.

Line Graph

A visual representation of data which shows change over time or in response to a manipulated variable.

Histogram

A visual representation of data, similar to a bar graph, which compares frequencies of different occurrences.

Standard Deviation

An average of how far each data point is away from the mean. A higher standard deviation indicates higher variability in the data (the data are more spread out). The Greek symbol sigma (σ) is used to represent standard deviation.

Categorical Data

Data recorded as categories/groups.

Quantitative Data

Data which is measured and usually expressed numerically. Ex: distance, time, temperature.

Mode

The most frequent number in a data set. Some sets of data have no mode (if all data values appear in the set the same number of times). Some sets of data have more than one mode (if multiple pieces of data in a set appear the same number of times and appear more than any other data values).

Range (stats)

The difference between the highest data value and the lowest data value.

Mean/Average

The mean is found by adding all of the numbers in a data set and dividing that sum by the number of numbers in the data set. The Greek symbol is often used to represent the mean.

Median

The median is found by first putting all the numbers in order from least to greatest. The median is either the middle number of a set that has an odd quantity of values, or, when there is an even number of values, the median is found by calculating the mean of the middle two numbers.

Stem-And-Leaf Plot/Stemplot

The plot where each data value is split into a "leaf" (usually the last digit) and a "stem" (the other digits). Stemplots are used for smaller sets of quantitative data. You can easily identify outliers, data clusters, or gaps on a stemplot.