Post on 18-Jan-2016
description
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2nd Year Practicals: Statistical Analysis Using E-Merge, E-Data Aid and EZ-ANOVA
Dr. Jonathan Stirk
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Repeated Measure Design-(Fully-Within Subjects)
Research Hypothesis: Does coping strategy influence pain?
Dependent Variable: Report of pain level 0..50 (0=no pain, 50=excruciating).
Independent Variables:– Coping strategy: Concentrate on Pain vs. Avoidance. – Time hand has been in ice water (3 levels: 30, 60, 90 sec).
8 subjects participate in all conditions (“repeated measures 2 x 3 design”)
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Individual data
0
5
10
15
20
25
30
35
40
45
1 2 3 4 5 6
Mary
Jane
Jill
Jean
Corey
Pam
Jennifer
Jersey
Concentrate Avoid
Individual Effects
Note: some individuals always report pain, others are very resistant. Repeated measure design reduces subject variability.
Time levels
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Group data / Interaction Graph
Group Effects
0
5
10
15
20
25
30
1 2 3
Time
Pa
in R
ati
ng
Concentrate
Avoidance
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ANOVA
Source SS df MS F P
Coping 46 1 46.02 1.87 0.213
related Error 172 7 24.54
Time 2140 2 1070.02 36.69 0.001
related Error 408 14 29.16
Coping*Time 288 2 144.02 21.09 0.001
related Error 96 14 6.83
Subjects 1055 7 150.74
• No main effect of coping strategy.
• Main effect of time: more time = more pain.
• Interaction: Avoidance better for short periods, but worse with longer intervals.
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Your data
For each individual, enter their mean score for each condition/cell into your analysis.
Analyse target present and target absent data separately. (only use 2-WAY ANOVA).
Use E-Merge, E-Data Aid & EZ-ANOVA / SPSS. If each factor has only 2-levels, no need for pairwise
comparisons. Interaction is probably important.
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Example data
Target Present DataStat 1 2 3 4
Familiar UnfamiliarSubject 4 Items 8 Items 4 Items 8 ItemsAlex 341 455 325 509Bob 423 515 401 501Corey 464 501 452 561Dave 505 532 485 578Eve 455 469 422 521Fred 431 533 461 559Gary 412 534 423 611Harriet 380 460 345 501
Repeat for Target Absent data (stat 5,6,7,8 data)
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Merging separate data files
Each subject run will create a single *.edat data file – E.g. ‘interlv-1-1.edat’, ‘interlv-2-1.edat’ etc.
Merge these into 1 large file using E-Merge This produces a merge file (*.emrg) You should open this merge file using E-Data
Aid
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Select Unmerged files (check they are all from the same experiment)
Click MERGE and name the merged file with something sensible
Ctrl-Left click will also choose each file
E-Merge
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E-Data Aid
Open E-data aid and open the merged file
You want to run separate analyses on the target present and target absent data, so choose filter (then checklist) and choose stat 1-4 or 5-8 (or whatever stat values are relevant for your exp’t if you have renumbered your cell conditions)
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Filtering Data
Once the filter is set your analysis will be limited to the Target Present or Absent subgroups
You may also want to analyse only RTimes from “correct” trials so filter using ‘STIMULUS.ACC’=1 and look at % errors too
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Analyse Data
To get the means for your data use the ANALYZE option in E-Data Aid (Looks like a calculator)
This will open the window seen on the right
– Row- Subject– Column- Stat– Data- Stimulus.RT
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E-Data ready for export / copy
This analysis provides the MEANS for the 4 conditions you selected
This can now be exported or copied to the clipboard ready to be analysed using EZ-ANOVA (or SPSS if you know how)
Just select the data and press Ctrl-C to copy
You may want to analyse median scores rather than means – double click on the data summary in previous window to alter
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EZ-ANOVA
Name your 2 factors (IV’s) e.g. Familiarity & Set Size (use max of 8 characters for factor & level names)
Set levels, choose number of rows (subjects)
Make sure you choose repeated measures design if it was
SetSz
4 8
FamiliarityFam 1 2
Unfam 3 4
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Results
ANOVA Table
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Interaction Graph
Target Present Trials
400
500
600
4 items 8 items
Set Size
RT
(m
s) Familiar
Unfamiliar
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EZ-ANOVA Plot
FamUnfam
500
600
700
800
Interaction Graph
4 8
Set Size
RT (msec)
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ANOVA help
For additional help on related (within-subjects) ANOVA see
– Keppel, G., Saufley, W.H.,Tokunaga, H. (1992) Introduction to Design and Analysis. (in library)
– Sprinthall, R.C.(2003). Basic Statistical Analysis, 7th Edition.– Howell, D. (1992). Statistical methods for psychology. – Dancey, C.P & Reidy, J. (2002). Statistics without maths for
psychology. – Or any other major stats text