Edexcel A2 Inferential Tests

•     By conducting an inferential test we are checking how far we can accept the null hypothesis.

- To asses the probability that the results are due to chance, an inferential statistical test is used.

-Inferential statistics tell us whether the difference between two sets of scores is significant or due to chance.

-In psychology, we accept the null hypothesis as the best explaination of out of results unless there is 5% probability or less of the results being due to chance.

• Nominal Data :- Categories

              Eg: Hot day or Cold day

• Ordinal Data :- Ranking

               Eg: How Hot or Cold (Ranked 1-10)

• Interval or Ratio :- Measuring

               Eg: Numerical (the exact numerical value)

>  Independent measures - An experimental design whereby each group involved contains different people. for every conditionof the experiment, a different group of participants will be used.

>  Repeated measures design - Where the same participants undergo all conditions of the study.

>  Matched pairs design - An independent measures design where the experimental groups are matched on important characteristics, eg: Background, Age, etc.

>  Correlation design - Where one participant provides data for two measures which are then tested to see if they show a relationship. There are two variables, (but not an IV or a DV) both are measured and both are of interest.    

You should be looking either

• For a Difference

or

• For a Correlation

• If a study looks for a correlation, it should be Spearman's Rank.

• It should contain Ordinal data

• The participant design should be a correlation design. 

• If a study looks for a difference, it can be a Chi-Squared test.

• It should contain Nominal data.

• The participant design should be Independent groups design.

• If you arw lokking for a difference, it can be Mann Whitney U test.

• It should contain Ordinal data.

• The participant design should be Independent groups.

• Identify the critical value; check 0.05 or 5%

If;

Calculated Value > Critical Value = Positive correlation

• Accept alternative/experimental hypothesis and reject null hypothesis 

And if;

Critical Value > Calculated Value = Negative Correlation

• Accept Null hypothesis and reject alternative/experimental hypothesis