Correlations

Question 1

Covarying variables

Answer 1

Two variables are correlated if they co-vary.

Positive or negative.

Question 2

Drawing correlations

Answer 2

Scatterplots gives information about:
Direction of relationship.
Form of relationship.
Degree of relationship.

Question 3

Line of best fit

Answer 3

Y= bX + a
b- gradient; every unit increase increases in X, Y increased by b.
a- Y intercept.

Question 4

Least square error

Answer 4

For every X value we can predict a Y value- known as Y^.
Residual= Y - Y^.
Square these for every X value and add them.

Question 5

Relationships

Answer 5

Don’t necessarily mean causation.
May be a third+ variable explaining the link- confounding variables that covert the the IV and explain the DV; extraneous variables.
Bidirectional links- DV may cause the IV and vice versa.

Question 6

Real life example

Answer 6

Huff (1954)- cancer was more common in places where more milk was consumed.
There is a positive correlation.
However this is because the average life expectancy was higher in countries where more milk was consumed.

Question 7

When to use correlation

Answer 7

When we want to see a relationship.
To explore mechanisms behind effects.
To establish how things are related.

Question 8

Tests of relationship

Answer 8

Correlation- measures the strength of relations ship between two variables.
Coefficient= r. Between -1 and +1.