Probability and significance

Question 1

What is a null hypothesis (H0 )?

Answer 1

Predicts there will be no effect between variables

Question 2

What is the alternative hypothesis (H1 )?

Answer 2

Predicts an effect between the variables (either directional or non-directional)

Question 3

What is significance?

Answer 3

The researcher can state that the relationship between the variables is due to more than just chance- they can accept the alternative hypothesis and reject the null hypothesis.

Question 4

What are inferential statistics?

Answer 4

A way of determining whether differences or relationships between variables are statistically significant or have occurred by chance.

Question 5

What is probability in the context of statistical testing?

Answer 5

The likelihood that the data obtained is due to chance (rather than manipulation of the IV).

Question 6

What is the usual level of significance used in Psychology?

Answer 6

p ≤0.05 (or 5%)

Question 7

When might psychologists adopt a more stringent significant level of 0.01?

Answer 7

• When there is a human cost- e.g. considering the effects of a new drug
• When the results are theoretically important

Question 8

What is a type I error?

Answer 8

Rejection of the null hypothesis when it should have been accepted (also known as a “false positive”, finding it significant when it wasn’t).

Question 9

What is a type II error?

Answer 9

Wrongly accepting the null hypothesis (known as ‘false negative’, finding it not significant when it was)

Question 10

When are researchers more likely to make a type I error?

Answer 10

When the significance level is too lenient (0.1 or 10%)

Question 11

When are researchers more likely to make a type II error?

Answer 11

When the significance level is too strict (0.01 or 1%)