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math vocab helping to prepare for the AP Stats test

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Median

Middle value. Usually used when data is skewed

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1st Quartile

25% of data lies below

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3rd Quartile

75% of data lies below

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Interquartile Range (IQR)

Q3-Q1

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5 Number Summary

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

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Mean

A measure of center used when data are symmetric

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Standard Deviation

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

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Time Plot

Displays data that change over time

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Parameter

A population measure

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Statistics

A sample measure that is calculated from a set of data

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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.

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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

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Response Variable

Variables that you hope to predict or explain (Y)

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Explanatory Variable

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

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Correlation Coefficient

A number that measures direction and strength of a linear association

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Lurking Variable

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

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Residual

Differences between data values and corresponding predicted values

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Slope

b₁ gives a value in Y units per X

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Intercept

b₀ is the value of Y when X is zero

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Sё

Standard deviation of residuals

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R²

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

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Extrapolation

When we use regression to predict the future

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Leverage

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

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Influential point

A point that when omitted will give very different results

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Ladder of Powers

Places an order to re-expression we must do

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Scatterplots

Shows relationship between two quantitative variables