Inferential Statistics

What You Need to Know for The Exam…. You will not have to conduct these tests in an exam(cue… sigh of relief) However you will have to; Know the purpose of using Inferential Statistics. Know what test you would use and why. Whether or not the results are significant?

Why are they used? 1)Statistical tests are used by Psychologists(and maths boffins) to prove or disprove a Hypothesis. 2) Statistical tests are used to determine whether data shows significance(if there is a relation or effect in the experiment). 3) Statistical tests see if the NULL Hypothesis is true(that results are due to chance/random). So the test is there to find out if the result was found by chance. 4) Which test you use depends on the data you have!

Choosing the Correct Statistical Test To decide what test you will use you need the following information: Difference/Correlation/Association: (This you will gather from the information given in the statement provided to you on the test. Type of Participant Design: Independent Measures, Matched Pairs, Repeated Measures Type of Data: NOIR They may refer to the terms parametric and non parametric on your exam.

  Nominal Ordinal/Interval/Ratio Test of association between two variables (correlation) Chi Squared Spearman’s Rho Test of difference: independent measures (two groups of different people are compared) Mann Whitney U test Test of difference: repeated measures (the same group of people are tested twice under two differing sets of conditions) xxx Wilcoxon

Time for the Tough Bit! Spearman Observed value of Rho Wilcox Observed Value T Mann-Whitney Observed Value or U Chi ² Observed Value of x ² The Observed Value refers to the statistical calculation that you carry out (this will always be given to you on the exam). The Critical Value is found on the critical tables, which you may need to work out on the exam using the critical value tables.

V. Whether or not the results are significant?   Spearman’s rho Chi square Mann Whitney U Wilcoxon T   rho≥C x²≥C U ≤ C T ≤ C

V. Whether or not the results are significant? The Observed Value refers to the statistical calculation that you carry out (this will always be given to you on the exam). The Critical Value is found on the critical tables, which you may need to work out on the exam using the critical value tables. Exam question type one: For the inferential statistical test you identified in question 6 explain how you will justify whether or not your results will be significant. The results of the Wilcoxon test will be significant if the observed value of T is ≤ than the critical value. Therefore the null hypothesis can be rejected and we can conclude that violent role models influence behaviour.

1. What is meant by P ≤ 0.025 2. State whether the researchers would reject the null hypothesis. 3. Explain your answer to B (i). You carried out a correlation study to see if there was a relationship between eating breakfast and student’s scores on a maths test. You carried out a Spearman's rho test on the data and found that the observed value of rho was +0.519 N= 20 (The observed value of rho must be equal to or greater than the critical table value to be significant.) p≤ 0.05 P ≤ 0.025 N= 20 0.380 .447

1. What test would you use? 2. State whether the researchers would reject the null hypothesis. 3. Explain your answer to B (i). Researchers tested the following hypothesis: There is a difference between a person’s score on a short term memory test when it is taken in the morning or in the afternoon. N=12 The observed value is: 26.5

1. Use the table decide whether the difference between males and females is significant. Explain how you reached your conclusion. A Mann-Whitney test on data produced by 8 male and 8 female participants produced an observed value of 16.3.

1. Use the table below to decide whether there is an association between a belief in the paranormal and a correct assessment of coincidences. 2. The researchers chose to use a significance level of p≤ 0.05. What does significance level mean?’ A Chi test on data produced by a two tailed hypothesis and the following table below produced an observed value of 1.984. High Low Total Right 5 12 17 Wrong 10 9 19 15 21 36