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RISKY SHIFT: DATA ANALYSIS

Learn how to test experimental hypotheses of the Risky Shift experiment using SPSS, produce graphs, interpret results, and write up discussion sections for your lab report. Explore the average level of risk across assessments and conduct tests for significance.

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RISKY SHIFT: DATA ANALYSIS

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  1. RISKY SHIFT: DATA ANALYSIS Week 6 Practical

  2. RISKY SHIFT WEEK 6 PRACTICAL LECTURE 1 PRACTICAL WEEK 1 NO LECTURE NO PRACTICAL WEEK 2 NONPARAMETRICS 1 1ST PRACTICAL WEEK 3 NONPARAMETRICS 2 1ST ANALYSIS IN SPSS WEEK 4 1ST ANALYSIS BY HAND SAMPLING DISTRIBUTIONS WEEK 5 2ND PRACTICAL WEEK 6 2ND ANALYSIS IN SPSS HYPOTHESIS TESTING WEEK 7 2ND ANALYSIS BY HAND RELATED T-TEST WEEK 8 3RD PRACTICAL INDEPENDENT T-TEST INDEPENDENT ANOVA WEEK 9 3RD ANALYSIS IN SPSS WEEK 10 DEPENDENT ANOVA NO PRACTICAL

  3. RISKY SHIFT LEARNING OUTCOMES BY THE END OF THE SESSION, YOU SHOULD BE ABLE TO: Use SPSS to test the first, second and third experimental hypotheses of Risky Shift experiment and produce related graphs. Make a graph to show the results with Excel 2007. Think about the meaning(s) of your results, how they relate to past research and how they could be flawed. Make a start on writing up your RESULTSandDISCUSSION sections for your lab report.

  4. RISKY SHIFT RESULTS These columns show mean risk score at PRE, GROUP and POST. The first 2 columns show participant id and group membership.

  5. RISKY SHIFT RESULTS Q1: Is the average level of risk different across the PRE, GROUP and POST assessments? RATINGS + WITHIN Ss + 3(+) GROUPS Friedman’s test First, we need to see whether there is any difference at all between the three groups, hence Friedman’s test. In SPSS, Friedman’s test is hidden away underneath nonparametric tests > K related samples.

  6. RISKY SHIFT RESULTS Q1: Is the average level of risk different across the PRE, GROUP and POST assessments? RATINGS + WITHIN Ss + 3(+) GROUPS Friedman’s test SPSS would like to know what the test variables are, and in our case we have three. Put premean, groupmean and postmean all into the test variable box. Under Test Type, make sure the Friedman test is ticked because there are other tests you can do.

  7. RISKY SHIFT RESULTS Q1: Is the average level of risk different across the PRE, GROUP and POST assessments? RATINGS + WITHIN Ss + 3(+) GROUPS Friedman’s test SPSS provides us with the mean ranks for each of the three groups. The test statistics box confirms our N, the chi-square value, the degrees of freedom (groups – 1) and the significance level. X2 (2) = 39.77, p < .001 The significance of this first test gives us the justification for going on to do the subsequent tests.

  8. RISKY SHIFT RESULTS Q2: Is the average level of risk recorded in the PRE assessment different from the risk recorded in the GROUP assessment? RATINGS + WITHIN Ss + 2 GROUPS Wilcoxon test Second, we need to see whether there is any difference between PRE and GROUP, hence Wilcoxon test. In SPSS, Wilcoxon test is hidden away underneath nonparametric tests > 2 related samples.

  9. RISKY SHIFT RESULTS Q2: Is the average level of risk recorded in the PRE assessment different from the risk recorded in the GROUP assessment? RATINGS + WITHIN Ss + 2 GROUPS Wilcoxon test Again, SPSS would like to know what the test variables are, and in our case we have a pair of variables. Put premean and groupmean into the test pair(s) box. Under Test Type, make sure the Wilcoxon test is ticked because there are other tests you can do.

  10. RISKY SHIFT RESULTS Q2: Is the average level of risk recorded in the PRE assessment different from the risk recorded in the GROUP assessment? RATINGS + WITHIN Ss + 2 GROUPS Wilcoxon test SPSS provides us with the positive, negative and tied ranks for variable pair. SPSS provides the Wilcoxon in the form of a z score to be reported as: Wilcoxon z = -5.18, p < .001, n = 41 Why 41 and not 48? SPSS ignored tied ranks…

  11. RISKY SHIFT RESULTS Q3: Is the average level of risk recorded in the POST assessment different from the risk recorded in the PRE assessment? RATINGS + WITHIN Ss + 2 GROUPS Wilcoxon test Second, we need to see whether there is any difference between POST and PRE, hence Wilcoxon test. In SPSS, Wilcoxon test is hidden away underneath nonparametric tests > 2 related samples.

  12. RISKY SHIFT RESULTS Q3: Is the average level of risk recorded in the POST assessment different from the risk recorded in the PRE assessment? RATINGS + WITHIN Ss + 2 GROUPS Wilcoxon test Again, SPSS would like to know what the test variables are, and in our case we have a pair of variables. Put premean and postmean into the test pair(s) box. Under Test Type, make sure the Wilcoxon test is ticked because there are other tests you can do.

  13. RISKY SHIFT RESULTS Q3: Is the average level of risk recorded in the POST assessment different from the risk recorded in the PRE assessment? RATINGS + WITHIN Ss + 2 GROUPS Wilcoxon test SPSS provides us with the positive, negative and tied ranks for variable pair. SPSS provides the Wilcoxon in the form of a z score to be reported as: Wilcoxon z = -5.15, p < .001, n = 40 Why 40 and not 48? SPSS ignored tied ranks…

  14. RISKY SHIFT RESULTS Q1: Is the average level of risk different across the PRE, GROUP and POST assessments? YES. Friedman's test X2 (2) = 39.77, p < .001 Q2: Is the average level of risk recorded in the PRE assessment different from the risk recorded in the GROUP assessment? YES. Wilcoxon z = -5.18, p < .001, n = 41 Q3: Is the average level of risk recorded in the POST assessment different from the risk recorded in the PRE assessment? Wilcoxon z = -5.15, p < .001, n = 40 YES. …but what are the direction of these effects?

  15. RISKY SHIFT RESULTS DOWNLOAD AND SAVE THE FILE ‘RISKYINEXCEL’ To calculate mean: =AVERAGE(cellab:cellcd) To calculate standard deviation: =STDEV(cellab:cellcd) To calculate standard error: =(cellSTDEV)/sqrt (no. observations) To start graphing: Select Insert → Column →

  16. RISKY SHIFT RESULTS SURPRISE! (So much easier than Excel 2003)

  17. RISKY SHIFT RESULTS • MAKING ERROR BARS • Select any part of the graph • Click on Layout (under Chart Tools on the toolbar) • Then Error Bars • Then More Error Bars Options Make sure you select all three standard errors.

  18. RISKY SHIFT RESULTS TIDYING UP Get rid of any unnecessary bits (e.g. background lines, legend) Change colours to greyscale Change the y-axis to reflect full range of possible answers Make sure you have axis labels

  19. RISKY SHIFT RESULTS LOW HIGH Q2: Is the average level of risk recorded in the PRE assessment different from the risk recorded in the GROUP assessment? Q3: Is the average level of risk recorded in the POST assessment different from the risk recorded in the PRE assessment? PRE > GROUP PRE > POST Lower risk (higher score) in PRE Lower risk (higher score) in PRE

  20. RISKY SHIFT DISCUSSION GET TOGETHER IN GROUPS OF THREE OR FOUR AND REFLECT ON TODAY’S EXPERIENCE USING THE FOLLOWING QUESTIONS Are there any problems with interpreting the data? What do the data actually tell me with respect to my experimental hypotheses? What implications do the data have for the studies outlined in the intro?

  21. RISKY SHIFT LEARNING OUTCOMES BY THE END OF THE SESSION, YOU SHOULD BE ABLE TO: Use SPSS to test the first, second and third experimental hypotheses of Risky Shift experiment and produce related graphs. Make a graph to show the results with Excel 2007. Think about the meaning(s) of your results, how they relate to past research and how they could be flawed. Make a start on writing up your RESULTSandDISCUSSION sections for your lab report.

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