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PLS 209 Research Methods pt 2
Dr. Aspin - Bradley University - Test 1 - Part 2
37
Plant Sciences
Undergraduate 3
02/24/2010

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Term
Definitions of Research Design (2)
Definition
Broad - The program that guides the investigator in the process of collecting, analyzing, and interpreting observations.
Narrow - A logical model of proof that allows the researcher to draw inferences concerning causal relations among the variables under investigation.
Term
Purpose of Research Design
Definition
Answer questions objectively, accurately, and in a timely manner.
Term
Natural Phenomenon vary in...
Definition
Whether or not they exist
Which of the multiple states is present
Or to what degree they exist in a given situation
Term
Variation
Definition
Sum of the squared deviations about the mean of a set of scores
Term
variance
Definition
Average squared deviation about the mean
Term
Systematic Variance
Definition
Variance in measures due to some known or unknown influences that "cause" the scores to lean in one direction more than the other. (There are real differences between the subjects.)
Term
Error Variance
Definition
Random fluctuations in measures due to chance. Not a real difference between subjects
Term
Total (observed) variance =
Definition
Systematic Variance + Error Variance
Term
Some systematic variance is labeled...
Definition
Error variance because of our ignorance of the causes of Y
Term
3 Criteria for Causal Inference
Definition
1. Temporal Order or Temporal Precedence
2. Co-variation of Cause and Effect
3. Internal Validity (No alt. explanation, non-spuriousness)
Term
Temporal Order/Temporal Precedence
Definition
Must show that cause X occurs before effect Y.
Active - can always estab. TO
Attribute - can sometiems estab TO, other times can infer it, and sometimes you can't.
Term
Co-variation of cause and effect
Definition
to what extent to values of x co-occur with values of y, OR to what extent does the presence of one variable correspond to the presence of another. (Do not truncate (shorten too much))
Term
Internal Validity
Definition
We must show there is no alternative explanation for the observed co-variation between x and y.
Term
intervening model
Definition
Model hypothesizing X1 having an indirect and not direct effect on Y
Term
Developmental model
Definition
Hypothesizes that X1 is not the original cause for Y, but is a conduit for its true cause X2.
Term
Spurious Cause
Definition
X2 occurs first, causing both X1 and Y
Term
Alternative cause model
Definition
There are other causes that cause Y (X2, X3, X4). You must show that X1 had an additional effect beyond them.
Term
Conditional Cause
Definition
Says you are partially right. Relationship only occurs under certain conditions
Term
External Validity
Definition
Ability to generalize from the empirical study to the real world.
Term
Qualities of Good Research design
Definition
1. Designed to answer research question
2. Maximize External Validity
3. Minimize Error Variance
4. Maximize Systematic/True Variance - allow variance to be observed.
IF CAUSAL HYPO, then these also
5. Establish temporal order variables
6. Control Systematic Extraneous Variables.
Term
3 components of classic research design (used to meet 3 criteria of cause and effect)
Definition
Manipulation
Comparison
Control
Term
Lesli Kish's 4 categories of variables for control purposes
Definition
1. Experimental Variables - those in the study
2. Controlled extraneous variables
3. uncontrolled extraneous variables which are empirically related to our experiment(the ones we are really worried about)
4. uncontrolled extraneous variables which are treated as randomized errors.
Term
4 types of control
Definition
Randomization
Limiting sample subset on control variable
Matching
Controlling in the statistical Analysis portion of the project
Term
degree of confidence
Definition
the more variables you remove from group 3 (uncontrolled extraneous variables relating to experimental variables) the more confident you can be in your causal relationship inference.
Term
Randomization
Definition
random selection of subjects and treatment groups.
moves all from group 3.
Term
Single Subgroup
Definition
limit sample to a single subgroup, limiting variance, therefore that group can no longer affect your variance. cost is not being able to generalize to population
Term
Matching
Definition
pair subjects based on the control variables and then randomly assign them to different groups.
Limited by finding matching subjects.
Term
Control in statistical Analysis
Definition
Put variable you want to control for in experiment as another independent variable, therefore controlling for it. Most often used in PLS.
Term
Alternatives to control
Definition
argument
observation measurement analysis
Term
2 types of research designs
Definition
experimental designs
Ex Post Facto designs
Term
Experimental Designs
Definition
power to manipulate the independent variable
power to randomly assign subjects and treatment groups
Strong in Causal inferrence (manipulatable) but weak in internal validity (too much control)
Term
ex post facto designs
Definition
lack either power to manipulate or power of randomization.
weak in causal inference (temporal sequence unnkown) but strong in internal validity (Measurements made in real world, have chance to notice other relationships.
Most common in social sciences
Term
Extrinsic threats to internal validity
Definition
differential (nonrandom) recruitment of subjects.
Term
Intrinsic threats to internal validity
Definition
Changes in subjects, measuring instrument, or reactive affect of observation.
History-all events that occurred during the time of the study that may affect it.
Maturation - developement - have a control group, both will develop the same.
Experimental mortality - drops out of study after pre-test but before post test.
Instrumentation - changes in measuring tool used
Testing - the process of being tested may change results.
Regression artifact - scores move closer to mean during post test.
Term
Factorial Design
Definition
Multiple Independent variables 4 group design (first group getting X1 and X2, second and third getting just X1, and last getting nothing.
Term
Solomon 4 block
Definition
4 group experiment design solves the problem of X1 only being exist or not exist, can do magnitudes of X
Term
Correlational Design
Definition
Multiple people same point in time (survey)
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