17 Dec 2010
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Oct.25th, 2010
Confound variable: An uncontrolled 3rd variable known to affect a relationship between two variables
Look at past studies to see if thereโ€™s any confounding factors already noticed ๎€ limitations of our study
GOAL: Find convergence in results among different studies
Randomization:
๎€How? randomly assign participants to do experimental/ control design, equally distributing the
differences among participants
๎€When? when the variables among participants cannot be held constant
๎€Why? Sampling the whole population = impossible, so we sample 1 population most of the time
(limited sample size)
๎€BUT, randomization may not beโ€ฆ
Easy/ Enough ๎€ because differences between subjects are too largeโ€ฆ
Evaluating Research:
Validity= truth and accurate representation of information
Construct Validity
๎€Adequacy of the operational definition of variables
๎€Are the results replicable?
Internal Validity
๎€Ability to draw conclusions about causal relationships from our data
*Experimental studies have higher chance b/c weโ€™re controlling variable, reducing possibilities of
confounds.
๎€Two general threats to internal validity:
1. when control groups are absent (non- experimental studies) b/c you have less power to
control study and come to conclusion based on collected date
2. when comparisons are made between โ€˜nonequivalent groupsโ€™ (Quasi-experimental: you
take subject groups as they are e.g: where victims live?) chances that differences between
the subjects maybe large enough to affect results
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External Validity = Extent to which the results can be generalized to other populations and settings
- Consider cohort effects (a group of ppl who were born in a specific time therefore experiencing )
the same life experience affecting them profoundly) /time of day effects
- Despite their artificial setting, lab experiments often have great value for understanding human
behavior.
Reliability: Consistency or Stability of a Measure of Behavior after re-testing
๎€‚Less Error
๎€Calculated as Pearson r
- Correlation coefficients called regression coefficients (reliability coefficient) used for ratio and
interval scales
๎€ƒCoefficients range from 0.00 to - 1.00 (variables covary in opposite directions) and 0.00 to +1.00
(variables vary in same direction)
๎€Testing for reliability:
1. Test-retest reliability:
-assessed by measuring the same individuals two points in time (subjects position in relative
distribution of scored should be similar to be reliable)
-Problems:
๎€ Vulnerable to artificially (participants start to figure out what the purpose of study itโ€ฆ
Hence change behavior)
๎€ Vulnerable to maturation (changes due to natural maturation of participants)
2. Internal Consistency Reliability
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Document Summary

Confound variable: an uncontrolled 3rd variable known to affect a relationship between two variables. Look at past studies to see if there"s any confounding factors already noticed limitations of our study. Goal: find convergence in results among different studies. how? randomly assign participants to do experimental/ control design, equally distributing the differences among participants. when? when the variables among participants cannot be held constant. Sampling the whole population = impossible, so we sample 1 population most of the time (limited sample size) Easy/ enough because differences between subjects are too large . adequacy of the operational definition of variables. ability to draw conclusions about causal relationships from our data. *experimental studies have higher chance b/c we"re controlling variable, reducing possibilities of confounds. 1. when control groups are absent (non- experimental studies) b/c you have less power to control study and come to conclusion based on collected date.

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