risky shift: data analysis week 6 practical. week 6 practicalrisky shift week 1 week 2 week 3 week 4...
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RISKY SHIFT:
DATA ANALYSIS
Week 6 Practical
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 1 PRACTICAL
NONPARAMETRICS 1 1ST PRACTICAL
NONPARAMETRICS 2 1ST ANALYSIS IN SPSS
SAMPLING DISTRIBUTIONS
1ST ANALYSIS BY HAND
HYPOTHESIS TESTING
2ND PRACTICAL
RELATED T-TEST
2ND ANALYSIS IN SPSS
INDEPENDENT T-TEST
INDEPENDENT ANOVA
DEPENDENT ANOVA
2ND ANALYSIS BY HAND
3RD PRACTICAL
3RD ANALYSIS IN SPSS
NO PRACTICAL
NO LECTURE NO PRACTICAL
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 2007.
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
RESULTS
The first 2 columns show participant id and group membership.
These columns show mean risk score at PRE, GROUP and POST.
RISKY SHIFT
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
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.
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.
Ranks
2.68
1.57
1.75
pre mean1_5
grp mean1_5
post mean1_5
Mean Rank
Test Statisticsa
48
39.767
2
.000
N
Chi-Square
df
Asymp. Sig.
Friedman Testa. X2 (2) = 39.77, p < .001
The significance of this first test gives us the justification for going on to do the subsequent tests.
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.
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.
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
Ranks
37a 22.38 828.00
4b 8.25 33.00
7c
48
Negative Ranks
Positive Ranks
Ties
Total
grp mean1_5 -pre mean1_5
N Mean Rank Sum of Ranks
grp mean1_5 < pre mean1_5a.
grp mean1_5 > pre mean1_5b.
grp mean1_5 = pre mean1_5c.
Test Statisticsb
-5.177a
.000
Z
Asymp. Sig. (2-tailed)
grp mean1_5- pre
mean1_5
Based on positive ranks.a.
Wilcoxon Signed Ranks Testb.
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…
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.
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.
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
Ranks
36a 21.94 790.00
4b 7.50 30.00
8c
48
Negative Ranks
Positive Ranks
Ties
Total
post mean1_5- pre mean1_5
N Mean Rank Sum of Ranks
post mean1_5 < pre mean1_5a.
post mean1_5 > pre mean1_5b.
post mean1_5 = pre mean1_5c.
Test Statisticsb
-5.150a
.000
Z
Asymp. Sig. (2-tailed)
postmean1_5 -
pre mean1_5
Based on positive ranks.a.
Wilcoxon Signed Ranks Testb.
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…
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 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?
Wilcoxon z = -5.18, p < .001, n = 41
YES.
YES.
YES.
…but what are the direction of these effects?
RESULTSRISKY SHIFT
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 →
RESULTSRISKY SHIFT
SURPRISE!
(So much easier than Excel 2003)
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.
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 answersMake sure you have axis labels
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 > GROUP PRE > POST
Lower risk (higher score) in PRE Lower risk (higher score) in PRE
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
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 2007.
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