Control

the heart of the experimental approach to knowledge is to ask the following two questions

1. what are the treats to the validity of a contemplated piece of research?

2. what means are available to neutralize those threats?

how is the concept of control used in psychology

1. standard of comparison

2. way of reducing variability

experimental group

subjects in an experiment who receive treatment

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

control condition

a condition in a within-subjects design experiment that does not contain the experimental manipulation

within-subjects experiment

research design in which each subject experiences every condition of the experiment

between-subjects experiment

research design in which each subject experiences only one of the conditions in the experiment

why do we reduce variability

limiting the things that change to those mandates by the experimental design reduces the chances of confounding variables or measurement error and increases our confidence in the experimental results

how are the two meanings of control related?

the primary meaning allows one to conclude that a dependent variable is associated with an independent variable and not with any other variable. the second usage facilitates drawing this conclusion by so limiting the number of variables operating in the situation and their range of values that the conclusion is clearer

how does control relate to the use of statistics?

we use inferential statistics to evaluate the probability that a difference between experimental and control groups or conditions is likely to have arisen by chance alone. second, we make enough observations or use enough subjects to reduce the variability of our estimate of the size of the experimental effect, and so make our statistical evaluation more precise