Lesson 9 Probability And Significance - Type I And Type II Errors

Question 1

What does the level of statistical significance mean?

Answer 1

Level at which decision is made to reject null hypothesis in favour of experimental one.

States how sure IV is having an effect on DV and not due to chance

Question 2

What is ‘chance’?

Answer 2

Something has no real cause and just happens

Question 3

What is probability?

Answer 3

Numerical measure that determines whether results are due to chance or real difference existing between experimental and control conditions

Question 4

What is the conventional and standard level of significance used in Psychology?

Answer 4

p<0.05

Question 5

Why is p<0.05 used?

Answer 5

Not too strict or lenient

Minimises chances of making Type I or Type II error

Question 6

What does a 5% level of significance show?

Answer 6

95% certainty that results show real difference between experimental and control conditions

Question 7

When are 5% significance levels often used?

Answer 7

There is a one-tailed directional hypothesis clearly stated in the research

Question 8

Why might a strict level of significance like 1% be used?

Answer 8

Research findings are CRITICAL and VERY IMPORTANT

Real difference MUST occur

E.g. Testing the effect of drugs on humans

Question 9

What is a Type I error?

Answer 9

Null hypothesis is rejected in favour of alternative hypothesis even though findings are due to chance

Probability of this happening is given by level of significance

Question 10

What is a Type II error?

Answer 10

Null hypothesis RETAINED even though alternative hypothesis is correct