Edexcel A2 Inferential Tests

This type of tests are used in the field of science (Eg: Mathematics, Biology as well as in Psychology) to analyse data statistically.

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  • Created by: Lochana
  • Created on: 16-03-12 18:55

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.

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Three Types of Data

  • 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)

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Participant Design

>  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.    

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In Inferential Tests

You should be looking either

  • For a Difference


  • For a Correlation
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Spearman's Rank 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. 
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Chi- Squared Correlation Coefficient

  • 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.
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Mann Whitney U Test

  • 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.
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Some Important Points

  • Identify the critical value; check 0.05 or 5%


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
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