Probability in Psychology (RM P2)

Question 1

What is the p≤0.05 significance level

Answer 1

• Means that there is a 5% probability that the effect seen is just chance (the IV is not actually affecting the DV)
• 95% of the time the behaviour is done
• 95% chance cannot be a fluke/coincidence

Question 2

Challenging other research

Answer 2

• When challenging well known theories, psychologists tend to adopt more stringent significance levels e.g p≤0.02 or p≤0.01 (only 1/100 fail to do this behaviour)

Question 3

Should the word proof ever be used in psychology?

Answer 3

• No, ‘proof’ implies 100% certainty
• This does not exist in psychological research, unless 100% accuracy is found (p=0.00 does not exist)
• p≤0.05 shows significant support for a theory but not proof

Question 4

What is a type 1 error?

Answer 4

• False positive
• Belief that a significant difference or correlation is found, but this is an error (one does not exist)
• Rejecting null hypothesis (when we shouldn’t, it’s actually true)

Question 5

What is a type 2 error?

Answer 5

• False negative
• Accepting a null hypothesis when you shouldn’t, it’s actually true

Question 6

How to avoid/reduce chances of making a type 1/2 error

Answer 6

• Making the significance levels stricter reduces change of T1 error (e.g p ≤ 0.01) but increases change of T2 error
• To reduce both, increase sample size