The most controversial type of experiment in the natural and the social sciences involve three major pairs of components, what are they?
1) Independent and dependent variables
2) Pretesting and posttesting
3) Experimental and control groups
Independent and dependent variables
IV- takes the form of an experimental stimulus that is either present or absent- that is having two attributes (EX)- concerning alcohol abuse, how often subjects use alcohol is the DV, exposure to the video about alcohol abuse is the IV.
Pretesting and Posttesting
simplest experimental design, subjects are measured by a DV (Pretest), exposed by a stimulus that represents a IV and than measured by a DV (Posttest)- difference between the first and the second measurement's on the DV are then attributed to the influenc
Experimental and control groups
Control groups are most evident in medical groups (Sugar pill example). Experimental group gets the alcohol video or medication. using control group allows researchers to control the effects of the experiment itself.
If both groups reduce alcohol use the
Double blind experiment
Is when neither the subjects or the experimenters know which is the experimental group or the control group (another researcher will know who is who but he or she will not be participating in the experiment itself) This allows researchers to separate the
Selecting subjects
Two basic decisions on who will participate?
First: decide target population, the group to which the results will apply.
second: decide how particular members of a target population will be selected for the experiment.
Randomization
Recruiting by whatever means, a group of subjects, we randomly assign those subjects to either an experimental or controlled group. EX. this may be done by numbering all subjects serially and selecting numbers by means of a random number table (odd number
experiments causal interface
The experimental design ensures: that the cause proceeds the effect in time by taking posttest measurements of the DV, after introducing the experimental stimulus.
Second Criteria: for causation- an empirical correlation between the cause and effect varia
The classical experiment makes it possible to satisfy this criteria for the cause in two ways:
1) The posttest measures for the experimental group (stimulus present) are compared with those for the control group (stimulus not present). If the observed correlation between the stimulus and the DV, is due to some other factor, then the two posttest sc
Threats to Validity
Refers to the problem that conclusions draw from experimental results may not accurately reflect what went on in the experiment itself.
Maturation
People are constantly growing and changing, whether in an experiment or not, those changes affect of outcome in the experiment.
longterm: subjects growing older and changing outcome.
short term: may become tired, bored, hungry
Testing
questionnaire measuring alcohol use, then we administer an experimental mental stimulus and remeasure their alcohol use. by the time we go to conduct a posttest the subjects may have been sensitive to the issue of alcohol use and provide different answers
Instrumentation
Concerns with changes in the measurement process itself. Always a problem in CJ research that uses secondary sources of information;such as, police record, court records, about probation violations. There may be changes in how probation violations are def
Selection Bias
Randomization elements the potential for systematic bias in selecting subjects, but subjects may be chosen in other ways that threaten validity.
Experimental Morality
Subjects often drop out of an experiment before it is completed, and that can affect statistical comparison and conclusion.
Statistical conclusion validity
Refers to whether we are able to determine if two variables are related
external validity
Represents a slightly different form of generalizability, one in which the questions whether results from experiments in one setting (time and place) will be obtained in other settings or whether a treatment found to be affective for one population will h
Threats to construct validity
Is the correspondence between the empirical test of a hypothesis and the underlying causal process that the experiment is intended to represent.
ambiguous causal time order
Is a CJ research, there may be ambiguity about the time order of an experimental stimulus and the DV. Whenever this occurs, the research conclusion that the stimulus caused the DV can be challenged with the explanation that the DV actually caused the chan