TERM

DEFINITION

Bar Graph

A data visualization tool that compares data across different categories or groups. It uses bars to present numeric values for levels of data categories, which can extend horizontally or vertically.

Pie Chart

A pie chart is a circular statistical graphic which is divided into slices to illustrate numerical proportion. In a pie chart, the arc length of each slice is proportional to the quantity it represents.

Two-way Table

A table that summarizes data on the relationship between two categorical variables for some group of individuals.

Marginal Relative Frequency

The percent or proportion of individuals that have a specific value for one categorical variable.

Joint Relative Frequency

The percent or proportion of individuals that have a specific value for one categorical variable and a specific value for another categorical variable.

Conditional Relative Frequency

The percent or proportion of individuals that have a specific value for one categorical variable among individuals who share the same value of another categorical variable (the condition).

Conditional Distribution

Side-by-side bar graph

Segmented bar graph

Mosaic plot

Association

Knowing the value of one variable helps us predict the value of the other.

No association

Knowing the value of one variable does not help us predict the value of the other.

TERMS

DEFINITION

Dotplot

Symmetric

Skewed right

Right side of the graph is much longer than the left side.

Skewed left

Left side of the graph is much longer than the right side.

Unimodal

Single peak

Bimodal

Two distinct clusters and peaks

Approximately symmetric

One peak, and the left and right sides are about the same (think of a hill).

Uniform

Frequencies are about the same for all values.

Stemplot

Histogram

Shows each interval of values as a bar. The heights of the bars show the frequencies or relative frequencies of values in each interval.

TERMS

DEFINITIONS

Mean

The average of all the individual values.

Statistic

A number that describes some characteristic of a sample.

Parameter

A number that describes some characteristic of a population.

Resistant

When a statistical measure isn’t resistant to extreme values.

Median

The number that is in the middle of the distribution.

Range

Maximum - minimum

Standard deviation

The typical value distance of the values in a distribution from the mean.

Sample variance

Sample Standard Deviation

Quartiles

Divisions in the distribution.

1st Quartile

The median of the values that are left of the actual median.

3rd Quartile

The median of the values that are right of the actual median.

Interquartile Range (IQR)

Q3 - Q1 = IQR

Outlier

Formulas:

Low outliers: Q1 - 1.5 x (Q3-Q1)

High outliers: Q3 + 1.5 x (Q3-Q1)

5 number summary

Minimum, Q1, Median, Q3, Maximum

Boxplot

Percentile (pth)

The value with p% of observations less than or equal to it.

Cumulative Relative Frequency Graph

A point corresponding to the percentile of a given value in a distribution of quantitative data. Consecutive points are then connected with a line segment to form the graph.

Standardized score (z-score)

IMPORTANT TO KNOW

z=value - meanstandard deviation or z=x-

TERMS

DEFINITIONS

Density Curve

Mean of a Density Curve

The point at which the curve would balance if made of solid material.

Median of a Density Curve

The equal-areas point, or the point that divides the area under the curve in half.

Skewed right - (mean > median) mean is closer to tail.
Skewed left - (mean < median) mean is closer to the first end.

Normal distribution

Symmetric density curves, single-peaked, bell-shaped

Normal Curve

Same thing as Normal distribution

Empirical Rule

(68-95-99.7)

68% - 1 standard deviation of the mean.

95% - 2 standard deviations of the mean.

99.7% - 3 standard deviations of the mean.

Standard Normal Distribution

Normal distribution with mean 0 and standard deviation 1.