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Statistics Test II

Terms

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The Purposes of Research Design
a. To provide answers to research questions b. To control variance or, in other words, to control for differences
An extraneous variable, also know as a confounding variable, will confuse the results of a study. An extraneous variable will affect the DV so that the researcher will not know if the changes in the DV are the result of changes in the IV or due to the inf
The Concept of Controlling Variance
o Randomization o Building Conditions or factors into the design as independent variables o Holding conditions or factors constant o Statistical adjustments
Four ways by which variance is controlled
o Random assignment of subjects to treatment groups – Random assignment of subjects to the control group and treatment groups is the most powerful method of experimental control available to a researcher. It is random assignment that distinguishes betwe
Randomization
This means making the extraneous variable an independent variable (IV). This is also called “Blocking.”
Building in Factors as Independent Variables
Holding the extraneous variable constant – If the researcher knows what the extraneous variables are, he or she may be able to hold them constant. For example, if I was attempting to bake some excellent bread and was experimenting with different ingredi
Holding Factors Constant
1. Freedom from Bias 2. Freedom from Confounding 3. Control of Extraneous Variables 4. Statistical Precision for Testing Hypotheses – statistical precision is increased when random or error variance is decreased.
Characteristics of Good Research Design
this means that neither the data nor the statistics used in the computation have any bias (systematic differences) in them. Bias would exist, for instance, if I were comparing cognitive-behavior therapy and hypnosis and put all the high-functioning indivi
Freedom from Bias
bias can enter the data through the confounding of variables. Suppose I wanted to know which of 3 RM&S textbooks would contribute to the highest NCE score in the research section. Bias could enter this data if I have 3 different professors each using one
Freedom from Confounding
extraneous variables are not the primary variables of interest in a research study. Nevertheless, they can influence the changes seen with the DV. Researchers, therefore, seek to control the influences of the extraneous variables.
Control of Extraneous Variables
Statistical precision is increased when random or error variance is decreased.
Statistical Precision for Testing Hypotheses
• A coach would probably not begin first down without a strategy. A contractor would probably not begin construction without a blueprint. You probably wouldn’t travel across the US in your car without a map. Strategies, blueprints, & maps are metaphor
The Meaning of Experimental Design
* Experimental variability * Extraneous variability * Error variability
3 Causes of Experimental Variability
Variability in the DV due to changes in the IV caused by the researcher
Experimental variability
Variability due to extraneous variables
Extraneous variability
Variability due to random fluctuations in the subjects, or the experimental conditions, or even the methods of measurement.
Error variability
* MAXimize experimental variability. * CONtrol extraneous variability. * MINimize error variability.
The optimal Research Design (MAX-MIN-CON)
Maximize experimental variability
This means to structure the experiment in such a way that any changes in the IV will show up as changes in the DV.
Control extraneous variability
This means that you want to structure the experiment so that there won’t be any extraneous variables affecting the DV.
Minimize error variability
This means that when you structure the experiment, you do so in a way that will try and minimize any fluctuations in the subjects, conditions, and measurement.

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