Y13 RESEARCH METHODS - probability ad significance

Question 1

what is the p value?

Answer 1

• represents probability
• between 0 and 1
• p value = close to one = results more likely happen by chance
• p value = close to 0 = less likely something happen by chance = can accept experimental hypothesis

Question 2

what are significance levels?

Answer 2

chosen value of ‘p’
5% sig level is p < 0.05 = 95% sure that results due to manipulation of IV
5% chance that that it was due to chance

Question 3

what is a Type I error?

Answer 3

• false positive
• rejecting a null hypothesis when we should not
• significant level is too high

Question 4

what is a type II error?

Answer 4

• false negative
• accepting a null hypothesis when we should not
• significance level is too low

Question 5

what is the critical value?

Answer 5

• when we carry out a statistical test, we obtain = calculated value
• IN SOME TESTS… calculated value > critical value
  or calculated value < critical value
• follow the rule of R

Question 6

what is the 3 criteria that the critical value depends on?

Answer 6

• one tailed/ two tailed hypothesis
• no of ps in the study ( N value)
• level of significance

Question 7

what is the rule of R

Answer 7

• statistical tests with the letter ‘R’ in their name are those where the calculated value must be greater or equal to critical value