Task 6: What time is it?

Question 1

The regression line is a

Answer 1

straight line that describes how a response variable y changes as an explanatory variable x changes.

Question 2

The regression line is used to

Answer 2

predict the value of y for a given value of x.

Question 3

The main difference between regression and correlation is that

Answer 3

correlation lets us know the association or the absence of a relationship between x and y.

Question 4

The formula of regression is:

Answer 4

y = b0 + b1x
b0 = intercept = y (bar) - b1*x(bar)
b1  = slope = r * sy/sx

Question 5

Extrapolation is

Answer 5

the use of a regression line for prediction far outside the range of values of the explanatory variable x used to obtain the line. Such predictions are not often accurate.

Question 6

The prediction errors we make are always error in the variable ..

Answer 6

y.

Question 7

error =

Answer 7

observed v. - predicted v.

Question 8

Because the slope and intercept of the least-squares line depend on the units of measurement =>

Answer 8

you can’t conclude anything from their size.

Question 9

The square of correlation r2 is the

Answer 9

variance of predicted y hat divided by the variance of predicted y.

Question 10

A residual is the

Answer 10

difference between an observed value of the response variable and the value predicted by the regression line.

Question 11

The mean of the least-squares residuals is always equal to

Answer 11

0.

Question 12

A residual plot is a

Answer 12

scatterplot of the regression residuals against the explanatory variable, that helps us asses the fit of a regression line.

Question 13

Association does not mean

Answer 13

causation.