Bivariate Data

Question 1

Define positive correlation

Answer 1

As one variable increases so does the other

r>0

Question 2

Define negative correlation

Answer 2

As one variable increases the other decreases

r<0

Question 3

Advantages of PMCC

Answer 3

It gives a number to represent linear correlation

Question 4

Disadvantage of PMCC

Answer 4

It does not mean anything if the data are not linear

Question 5

When do you use Spearman’s rank

Answer 5

The data do not follow a linear pattern

Subjective

Question 6

When do you use PMCC

Answer 6

Data must be objective
Data must follow a linear pattern on the scatter diagram

Question 7

Advantage of spearman’s rank

Answer 7

It always means something

Question 8

Disadvantage of Spearman’s rank

Answer 8

Can not determine if the association is linear or not

Question 9

What happens if you shift or stretch PMCC or Spearman’s rank data

Answer 9

r and rs will stay the same

Question 10

Is correlation a causation

Answer 10

No

Correlation is not a causation

There may be a third factor involved

Question 11

What is the equation for the least square regression line

Answer 11

y=a+bx

Question 12

What does the letter a in the least square regression line mean

y=a+bx

Answer 12

The expected y value when x = 0

Question 13

What does the letter b mean in the least square regression line

y=a+bx

Answer 13

Expected increase in y for every increase of 1x

Question 14

What does it mean when the residuals are small (r is close to 1 or -1)

Answer 14

The regression line may be a good fit and give reliable predictions

Question 15

What does interpolation mean

Answer 15

When you predict using values that are within the range of the data cancelled

Question 16

What does extrapolation mean

Answer 16

When you predict using values outside the range of data collected