probability and significance

Question 1

probability

Answer 1

The likelihood that a particular event will occur.
0 = statistical impossibility
1 = statistical certainty

Question 2

significance

Answer 2

Tells us how sure we are that a difference or correlation exists.

Question 3

statistical test

Answer 3

The statistical test that is carried out determines which hypothesis is likely to be correct and therefore whether the null hypothesis can be accepted or rejected.
Statistical tests work on the basis of probability rather than certainty.
All tests use a significance level which is the point which the researcher can claim to have discovered a significant difference or correlation within the data - the point at which the null hypothesis can be rejected and therefore the null hypothesis accepted.

Question 4

level of significance

Answer 4

The usual level of significance in psychology is 0.05 (5%).
This means the probability that the observed effect occurred by chance is equal to or less than 5%, therefore when researchers claim to have found a significant difference or correlation there is still up to 5% probability that the observed effect occurred by chance.