*c. State whether Bianco and Lecce (2016) should use a one or a two tailed test when checking for significance and why (2)*

They would use a one tailed test because the text states that Bianco and Lecce (2016) believe they can improve children’s Theory of Mind test scores in just 4 x 50 minute sessions. This suggests that they would have had a directional hypothesis predicting that test scores will be better after the intervention than before.

*d. State the appropriate critical value (1)*

The correct critical value for a one tailed test at the 0.05 level when N=9 is 8.

This exam question used command term state so you don’t need to say why this is the correct critical value, however I thought a brief explanation would help as finding N is a little different to some of the other tests and is not very well explained in the Edexcel instructions; basically N = the number of Pps where there was a difference between their two scores. So if there was no difference as both scores were exactly the same, then their D score would be zero. This means they no longer are counted when working out N. In this example, every Pp had difference between their scores and so N was 9 as none of the scores were discounted.

*e. State whether Bianco and Lecce (2016) would reject the null hypothesis based on this analysis and why (3)*

Bianco and Lecce (2016) would not reject the null hypothesis. They would accept the null and reject the experimental hypothesis, as the observed value of 9 is greater than the critical value of 8. This means that the probability that the null is correct or that results are due to chance is greater than 1 in 20.

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