Median

Middle value. Usually used when data is skewed

Range

High-Low

1st Quartile

25% of data lies below

3rd Quartile

75% of data lies below

Interquartile Range (IQR)

Q3-Q1

5 Number Summary

Same as a box and whisker plot (min, max, Q1, Q3, Median)

Mean

A measure of center used when data are symmetric

Standard Deviation

Measure of Spread - tells the average distance each value is away from the mean

Time Plot

Displays data that change over time

Parameter

A population measure

Statistics

A sample measure that is calculated from a set of data

Z-Score

Tells how many standard deviations a value is away from the means. They do not have units, so we can compare two different values.

65-95-99.7 Rule

Says 68% fall within 1 standard deviation, 95% of data fall within 2 standard deviations, 99.7% of data fall within 3 standard deviations

Response Variable

Variables that you hope to predict or explain (Y)

Explanatory Variable

Variables that you can use to account for, explain or predict the Y variable (X)

Correlation Coefficient

A number that measures direction and strength of a linear association

Lurking Variable

A variable other than X and Y that affects both variables accounting for the correlation between the two

Residual

Differences between data values and corresponding predicted values

Slope

b₁ gives a value in Y units per X

Intercept

b₀ is the value of Y when X is zero

Sё

Standard deviation of residuals

R²

Overall measure of how successful the regression is in linearly relating Y to X

Extrapolation

When we use regression to predict the future

Leverage

Data points that pull the line lose to them so they can have a great effect on slope and intercept

Influential point

A point that when omitted will give very different results

Ladder of Powers

Places an order to re-expression we must do

Scatterplots

Shows relationship between two quantitative variables