Chapter 3

Question 1

response variable

Answer 1

measures the outcome of a study (y)

Question 2

explanatory variable

Answer 2

may help predict/explain changes in a response variable (x)

Question 3

scatterplot

Answer 3

displays the relationship between two quantitative variables measured on the same individuals, one goes on the x axis other on y axis

Question 4

positive association

Answer 4

two variables have a positive association when the values of one variable increase as the values of the other variable increase as well

Question 5

negative association

Answer 5

two variables have a negative association when the values of one variable decrease while the values of the other variable increase

Question 6

no association

Answer 6

there is no association between two variables if knowing the values of one variable do not help predict the values of the other variable

Question 7

correlation (r)

Answer 7

for a linear association, between two quantitative variables, this measures the direction and strength of the association
can only be between -1 and 1

Question 8

regression line

Answer 8

models how the response variable changes as the explanatory variable changes

Question 9

extrapolation

Answer 9

exaggeration, out of the data range

Question 10

residual

Answer 10

difference between actual y value and the predicted y value
AP = actual - predicted

Question 11

least squares regression line

Answer 11

line that makes the sum of the squared residuals as small as possible

Question 12

residual plot

Answer 12

scatterplot with residuals on x axis and explanatory variable on the y axis

Question 13

standard deviation of residuals

Answer 13

s measures the typical distance between the actual y value and the predicted y value (also known as y hat)

Question 14

coefficient of determination of r^2

Answer 14

measures the percent of variability in the response variable that is accounted for by the least squares regression line

Question 15

high leverage

Answer 15

points with much larger/smaller x values than other data points in the regression

Question 16

outlier

Answer 16

a point that does not follow the patter of the data
has a larger residual compared to other data points

Question 17

influential points

Answer 17

any point that would significantly change the slope, y intercept, the correlation, coefficient of determination, or the standard deviation of residuals

Question 18

b = r x sy/sx

Answer 18

slope = correlation(standard deviation of y/ standard deviation of x)
use this to find the slope

Question 19

describing a scatterplot (DUFS)

Answer 19

Direction – positive/negative
Unusual pattern – outliers
Form – linear/nonlinear
Strength – strong/moderate/weak
Like DUFF Beer