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Part I: 14 July 2011
Toronto Rehab
550 University Ave.
Manolo Romero Escobar
http://mixedReviews.wordpress.com
14/07/20111
Quantitative Data Analysis
for Health Research
Your type of question
14/07/20112
Descriptive
Relational
Causal
Your type of design
14/07/20113
Passive-Observational
Quasi-experimental
Experimental
Types of experimental designs
14/07/20114
Type Observation Treatment Observation Treatment Observation
Basic: X O
O
Factorial X(A1B1)
X(A1B2)
X(A2B1)
X(A2B2)
O
O
O
O
Pre-test
Post-test
O
O
X O
O
Solomon Four
Group
O
O
X
X
O
O
O
O
Switching
Replications
O
O
X O
O X
O
O
Crossover O
O
X(A)
X(B)
O
O
X(B)
X(A)
O
O
Longitudinal O...O X O. O...O
Types of control groups
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Placebo Expectancy Wait-list
AttentionNo-
Attention
Sampling and the sampling distribution
Central Limit Theorem Applet
http://www.cs.uic.edu/
~wilkinson/Applets/clt.
html
14/07/20116
Levels of SES
Treatm
en
t C
on
dit
ions
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Control Emotion Focus Empowrmnt
46
810
12
14
Self
-Est
eem
Treatment Condition
5 10 15 20
46
810
12
14
Resilience)
Self
-Est
eem
Categorical variables
Testing mean differences of a continuous variable
between groups (categorical variable)
Continuous variables
7
Mean contrast & ANOVA
14/07/20118
2 groups: t-test
Independent Samples
Repeated Measures
k groups: ANOVA
One way ANOVA
One-way Repeated Measures
Factorial (e.g. 2x2)
Repeated Measures Factorial
Extensions to the factorial design
14/07/20119
• Levels as in T1, T2, control.
• Factors: Main effects: A, B, C
• Interactions: AB, AC, BC, ABC
Add levels/factors
• Non-random (e.g. Gender) factor
• Sometimes better to use ANCOVA (GLM)
Blocking factor
• Within-Between effects
• Issues with assumptions: homogeneity of variance (sphericity)
• Corrections: Geisser-Greenhouse & Huynh-Feldt.
Repeated measures
factor
ANOVA, ANCOVA, Regression,χ2
14/07/201110
Method Dependent Independent
ANOVA Continuous Categorical
ANCOVA Continuous At least one
categorical and
one continuous
Multiple
Regression (MR)
Continuous
(linear) or
categorical (e.g.,
logistic)
Continuous or
categorical
(dummy coded)
χ2 test of
independence
Categorical Categorical
Parametric Effect Size Indexes
From Kline 2004
Links on the website:
http://mixedreviews.wordpress.com/2011/07/13/quantitative-data-analysis-part-i/
14/07/201111
G*Power 3
http://www.psycho.uni-
duesseldorf.de/abteilung
en/aap/gpower3
14/07/201112
G*Power 3: Mean contrasts
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�One group:
�Difference from constant
� Two groups:
�Two dependent groups, matched pairs
�Two independent groups
�Many groups:
�ANOVA: One-way (one independent variable)
�ANOVA: Main effects and interactions (two or
more independent variables)
14/07/201114
Exercise 1: t-testt-test: Independent
samples
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� Calculate sample size with
the parameters presented
� Plot sample size (y axis) as
a function of effect size
(use values of d from .2 to
.8)
14/07/201116
Tota
l sam
ple
siz
e
Exercise 2: F test
14/07/201117
DV: Self Esteem
Treatment
Groups
mean sd n
Control 7.63 1.50 40
Emotion Focus 11.43 2.11 40
Empowerment 9.73 1.75 40
SES Groups mean sd n
low 8.84 2.36 32
medium 9.66 2.32 59
high 10.28 2.34 29
� One way ANOVA omnibus
test
� Estimate the effect size for
each IV groups
� With power of .80
determine sample size
Recommended