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Lecture 1

# SOAN 2120 Lecture Notes - Lecture 1: Random Number Generation, Equivalent Average, Random Assignment

Department
Sociology and Anthropology
Course Code
SOAN 2120
Professor
D Walters
Lecture
1

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SOAN2120
Experimental Designs
Experimental Research- Chapter 7
Independent variable -> dependent variable (differences in outcomes
between two groups)
Equivalent
-average scores on the dependent variable and
-scores on all other variables which are likely to impact the dependent
variable
Differences: manipulation
If there are different results it is because of different treatments
How do we establish the equivalence of two (or more) groups?
Random number generator
Objective: equal probability of assignment
Essential the groups are equivalent
Conclusion: Manipulation
Event with RA the two (or more) groups will not be exactly in all respects.
Random individual variations).
If the assignment is random, we can use tests of statistical significance
(manipulation vs. random variation)
As the sample size increases, individual differences decline
Without RA: Findings may be attributable to pre-existing differences
between the groups
What is this called>
We could compare pre-test scores (dependent variable measures) before the
experiment begins
-Significantly different? ->equivalent -> proceed as if random assignment
What about all other potential confounding variables?
This happens automatically with random assignment
Standard Notation: pg173
R O1 X O2
R O3 O4
X represents an experimental variable or effect the independent variable
O represents a dependent variable observation. Subscripts (scripts) depict
the observation; the exact ordering of the numbering is somewhat
unimportant
This experiment has a pre-test and a post-test
The pre-test for the experimental group (O1)
The pre-test for the control group (O3)
Finally, the letter R denotes RA
Simulated driving video game to assess the impact of various substances on
driving impairments
Group 1; 6 crashes (weed)
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