Lecture 2 Correlation

Question 1

What does a correlation of 0 indicate?

Answer 1

No association

Question 2

What is a small effect according to Cohen?

Answer 2

.10

Question 3

What is a medium effect according to Cohen?

Answer 3

.30>r>.50

Question 4

What is a large effect according to Cohen?

Answer 4

R>.50

Question 5

What is an example of a perfect linear relation?

Answer 5

For every change in the X variable, there will be a corresponding change in the y variable

Question 6

What is r squared?

Answer 6

The proportion of variance shared by two variables.. (Percentage)

R squared is pretty much how much one variable explains the other.

Also tells us what we don’t know (percentage of variance not explained by r2)

Question 7

What is the null hypothesis for correlations?

Answer 7

That the correlation in the population is zero

Question 8

When do you reject null hypothesis?

Answer 8

When p is LESS THAN .05

Ask what is the probability of finding r this big, if the real association of the population is zero?

Question 9

What is r and what is ‘rho’

Answer 9

R is the correlation in the same

Rho is the correlation in th population

Question 10

What is the df for correlations

Answer 10

Df= n-2

Question 11

Range of a correlation coefficient can be?

Answer 11

-1 to 1

Question 12

When can spearman correlation coefficient be used?

Answer 12

Rs

When data is ordinal (ranked)

And when data is one directional but not linear

Can use with outliers or skewed data

Formula: convert data to ranks and apply pearsons formula