W8 - Effect Size

Question 1

What do inferential statistics allow us to do?

Answer 1

Make conclusions about the pop based on sample statistics

Question 2

What can be HIGHLY influenced by the sample size

Answer 2

The p-value

Therefore whether the data shows it as being statistically different or not/

Question 3

Explain sample size + statistical significance

Answer 3

Very large sample size = Possible to get a significant effect when the real effect is very small

Question 4

What does a larger sample size result in for the representativeness of the sample of the population

Answer 4

Larger sample size = More representative the sample of the pop

Question 5

Larger sample size = More representative the sample of the pop

What follows?

Answer 5

Lower risk of sampling bias = ⬆️ reliability from a small effect

Question 6

Why is an effect size created?

Answer 6

To determine whether something is PRACTICALLY significant + meaningful in the real world.

Question 7

What can effect size facilitate with?

Answer 7

Comparison of effect across studies

Question 8

What is an estimate of effect size?

Answer 8

Correlation coefficient (r)

Question 9

What can Cohen’s D be used for?

Answer 9

To look at whether the difference between the 2 means of 2 groups is meaningful or not.

Question 10

When would you use Cohen’s D?

Answer 10

When focus is on difference between 2 means

Question 11

Cohen’s D equation

Answer 11

D = (M1-M2) / SD

Question 12

What can the SD in the Cohen’s D equation be?

Answer 12

Pooled = SD in total sample

OR

SD of control group / condition

Question 13

In what ways can we interpret the Cohen’s D size?

Answer 13

In terms of small, medium or large effect

Question 14

Small effect size for the r value and the D value

Answer 14

r = 0.1

D = 0.2

Question 15

Medium effect size for the r value and the D value

Answer 15

r = 0.3

D = 0.5

Question 16

Large effect size for the r value and the D value

Answer 16

r = 0.5

D = 0.8

Question 17

What is another way to calculate an effect size?

Answer 17

By converting a t-statistic into a Pearsons correlation coefficient (r)

Question 18

Equation to calculate effect size by converting a t-statistic to Pearsons correlation coefficient

Answer 18

r = square root of ( t^2 / t^2 + df)

Question 19

Provide reasons why its important to report effect size (3 marks)

Answer 19

Indicates whether the effect matters in the real world

Objective + standardised measure of magnitude of effect

Facilitates comparison of effect across studies

Question 20

When looking at SPSS data, what table would you look at to describe the relationship between the 2 variables?

What data would you provide in your answer?

Answer 20

Correlations table showing:

Pearsons correlation

Sig. (2 tailed)

N

i.e answer = Moderate to strong significant positive relationship, r = 0.480 and p<0.05

Question 21

How would you answer this question?

What is the regression equation for these variables?

Answer 21

Y= a + bX

Then work it out

(Look at the coefficients table)