Unit 2 Flashcards
2 variables are associated if…
The outcome of the first affects the outcome of the second
How to describe scatter plot
- Direction
- Form
- Strength
- Outliers
Linear regression equation (and when it can be used)
Ŷ=a+bx (can only be used on linear graphs, and can’t use Y to predict X)
Residual equation
Y-Ŷ
A … graphed residual plot implies a linear model
Randomly
When is a linear model appropriate?
- If there is a line pattern
- The residual plot is random
Find the slope in the linear regression equation (b)
b = r x (std y / std x)
or
correlation x (stndev of y values / stndev of x values)
Find (a) in linear regression equation
a = y bar - b(x bar)
(mean of y values) - (b)(mean of x values)
Define correlation
The strength and direction of the linear relationship between 2 QUANTITATIVE variables
P(brown eyes) is an example of a … frequency
Marginal
P(brown eyes | male) is an example of a … frequency
Conditional
2 ways to determine linear reliability
- Coefficient of determination (r^2 you want to be closer to 1.0/100%)
- Standev of residuals (s)
Outlier in regression
Outlier in a Y value; doesn’t change slope much
Outlier in leverage
Outlier in X value; changes slope significantly
Influential point
Outlier that, when added or taken away, significantly changes slope
