18.4 — pearson’s correlation coefficient

Question 1

what is correlation?

Answer 1

the relationship between two variables

Question 2

what are the types of correlation and what is the relationship between the variables?

Answer 2

1. positive — when both variables increase or decrease together
2. negative — when one variable increases as the other decreases
3. non existent — when there is no clear relationship, indication by a correlation coefficient close to 0

Question 3

what does a correlation coefficient of 1 indicate?

Answer 3

a perfect, positive linear correlation where all points lie on a straight line

Question 4

what does Pearson’s correlation coefficient assess?

Answer 4

the strength and direction of a linear relationship between two continuous variables that are normally distributed

Question 5

what is the process for calculating Pearson’s correlation?

Answer 5

1. calculate the mean of each variable
2. subtract the mean from each observed value
3. square the values from step 2
4. multiply together the values calculated in step 2
5. sum the values calculated in steps 3 and 4

Question 6

what does an r value near +1 indicate?

Answer 6

a strong, positive correlation

Question 7

what deos an r value near -1 suggest?

Answer 7

a strong, negative correlation

Question 8

what does an r value around 0 imply?

Answer 8

there is no correlation