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RISKY SHIFT: DATA ANALYSIS Week 6 Practical

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WEEK 6 PRACTICALRISKY SHIFT WEEK 1 WEEK 2 WEEK 3 WEEK 4 WEEK 5 WEEK 6 WEEK 7 WEEK 8 WEEK 9 WEEK 10 LECTURE 1PRACTICAL NONPARAMETRICS 11 ST PRACTICAL NONPARAMETRICS 21 ST ANALYSIS IN SPSS SAMPLING DISTRIBUTIONS 1 ST ANALYSIS BY HAND HYPOTHESIS TESTING 2 ND PRACTICAL RELATED T-TEST 2 ND ANALYSIS IN SPSS INDEPENDENT T-TEST INDEPENDENT ANOVA DEPENDENT ANOVA 2 ND ANALYSIS BY HAND 3 RD PRACTICAL 3 RD ANALYSIS IN SPSS NO PRACTICAL NO LECTURENO PRACTICAL

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

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

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RESULTS 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. Q1: Is the average level of risk different across the PRE, GROUP and POST assessments? RISKY SHIFT Friedman’s testRATINGS + WITHIN Ss + 3(+) GROUPS

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RESULTS Q1: Is the average level of risk different across the PRE, GROUP and POST assessments? RISKY SHIFT Friedman’s testRATINGS + WITHIN Ss + 3(+) GROUPS 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.

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RESULTS Q1: Is the average level of risk different across the PRE, GROUP and POST assessments? RISKY SHIFT Friedman’s testRATINGS + WITHIN Ss + 3(+) GROUPS 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. X 2 (2) = 39.77, p <.001 The significance of this first test gives us the justification for going on to do the subsequent tests.

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RESULTS Q2: Is the average level of risk recorded in the PRE assessment different from the risk recorded in the GROUP assessment? RISKY SHIFT Wilcoxon testRATINGS + WITHIN Ss + 2 GROUPS 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.

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RESULTS Q2: Is the average level of risk recorded in the PRE assessment different from the risk recorded in the GROUP assessment? RISKY SHIFT Wilcoxon testRATINGS + WITHIN Ss + 2 GROUPS 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.

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RESULTS Q2: Is the average level of risk recorded in the PRE assessment different from the risk recorded in the GROUP assessment? RISKY SHIFT Wilcoxon testRATINGS + WITHIN Ss + 2 GROUPS 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…

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RESULTS Q3: Is the average level of risk recorded in the POST assessment different from the risk recorded in the PRE assessment? RISKY SHIFT Wilcoxon testRATINGS + WITHIN Ss + 2 GROUPS 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.

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RESULTS Q3: Is the average level of risk recorded in the POST assessment different from the risk recorded in the PRE assessment? RISKY SHIFT Wilcoxon testRATINGS + WITHIN Ss + 2 GROUPS 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.

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RESULTS Q3: Is the average level of risk recorded in the POST assessment different from the risk recorded in the PRE assessment? RISKY SHIFT Wilcoxon testRATINGS + WITHIN Ss + 2 GROUPS 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…

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

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RESULTSRISKY SHIFT DOWNLOAD AND SAVE THE FILE ‘RISKYINEXCEL’ To calculate mean: =AVERAGE(cell ab :cell cd ) To calculate standard deviation: =STDEV(cell ab :cell cd ) To calculate standard error: =(cell STDEV )/sqrt ( no. observations ) To start graphing: Select Insert → Column →

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RESULTSRISKY SHIFT SURPRISE! (So much easier than Excel 2003)

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RESULTSRISKY SHIFT 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.

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RESULTSRISKY SHIFT 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

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

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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 implications do the data have for the studies outlined in the intro? What do the data actually tell me with respect to my experimental hypotheses? RISKY SHIFT

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

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