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9 Cards in this Set
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16.What does the concept of control mean in experimentalresearch? |
control: any means used to rule out threats to the validity of research
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17.Distinguish the meanings of control: control experimentand experimental control. |
The first and fundamental meaning of the term control is that of providing a standard against which to compare the effect of a particular independent variable. control group: subjects in a between-subjects design experiment who are like the experimental group in every respect except that they do not receive treatment Instead of having different subjects experience each condition, in some experiments each subject experiences every condition. In such an experiment, instead of having a control group, we have a control condition. Control condition: a condition in a within-subjects design experiment that does not contain the experimental manipulation within-subjects |
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18.List several specific strategies for achieving control. |
Subject as Own Control (Within-Subjects Control). One of the most powerful control techniques is to have each participant experience every condition of the experiment. In this way, variation caused by differences between people is greatly reduced.
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19.Briefly describe the strategy of subject as own control.What are the limitations of this strategy? |
One of the most powerful control techniques is to have each participant experience every condition of the experiment. In this way, variation caused by differences between people is greatly reduced. In many experiments, however, using subjects as their own controls simply is not possible. The information cannot be unlearned, so using the subjects as their own controls is not possible. Another situation in which using subjects as their own controls is not feasi- ble occurs when contrast effects exist between the conditions of the experiment, so that experiencing one condition may carry over and influence the response to another condition. These contrast effects, also known as order and sequence effects. For instance, if magnitude of reward is the independent variable, subjects who experience a large reward (say, $200) first may respond less to a small reward (say, $20) than they would have if only the small-reward condition had been received. |
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20.What is random assignment? How can random assignment beperformed? |
Another powerful control method is random assignment of subjects to groups in a between-subjects experimental design. The term random assignment, or random allocation, is used here in a specific sense: The allocation of subjects to conditions is random when each subject has an equal and independent chance of being assigned to every condition. |
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21.Why is matching a strategy for achieving control? Underwhat conditions should matching of subjects be done? Describe the propermatching procedure. |
Experimental precision can sometimes be improved by matching subjects on a pretest before randomly allocating them to conditions. When the subjects differ among themselves on an independent variable known or suspected to affect the dependent variable of interest, matching may be necessary. Generally, you try to match on the basis of some variable that has the highest possible correlation with the dependent variable. Normally, the highest correlation is between the dependent variable and itself. In other words, if you are doing an experiment using reaction time, matching subjects according to their reaction times makes the most sense. |
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22.Briefly describe building nuisance variables in anexperiment as a strategy for achieving control. |
In addition to random assignment or matching, another way to handle variables that cannot easily be removed from the experiment is to design the experiment so that these nuisance variables become independent variables in the study. Nuisance variables are known or suspected to affect the dependent variable, but variables in which you have no theoretical interest. Left uncontrolled, these variables may affect the dependent variable so strongly that they hide the true effects of the independent variable.
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23.How is statistical control used as a strategy forachieving control? |
Except for randomization, all the control methods described so far can be classified as methods of achieving experimental control; they aim to reduce variability as much as possible. Usually, however, that old devil variability cannot be completely exorcised from the experiment. Then it is necessary to use statistical control. Statistical control in the broad sense is synonymous with inferential statistics, the branch of statistics that deals with making decisions in the face of uncertainty.
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24.What is replication? Distinguish two types ofreplication: direct and systematic. |
replication: repeating an experiment to see if the results will be the same. Two types of replication are commonly distinguished: direct and system- atic. Direct replication occurs when someone repeats essentially the identical experiment in an attempt to obtain the same results. Systematic replication occurs when Researcher B says, “If A’s theory is correct, then the following should happen.” Then B performs an experiment different from A’s but based on it. If A’s results and theory are correct, B should find a result that supports the theory. |
