Experimental Research Strategy PDF

The Experimental Research Strategy  1. Cause-and- Effect Relationships 2 ▣ experimental research strategy establishes the existence of a cause-and-effect relationship between two variables. To accomplish this goal, an experiment manipulates one varia...

The Experimental Research Strategy  1. Cause-and- Effect Relationships 2 ▣ experimental research strategy establishes the existence of a cause-and-effect relationship between two variables. To accomplish this goal, an experiment manipulates one variable while a second variable is measured and other variables are controlled. ▣ experiment or a true experiment attempts to show that changes in one variable are directly responsible for changes in a second variable. 3 four basic elements: 1. Manipulation. The 3. Comparison. The scores researcher manipulates in one treatment one variable by changing condition are compared its value to create a set of with the scores in another two or more treatment treatment condition. conditions. 4. Control. All other 2. Measurement. A second variables are controlled to variable is measured for a be sure that they do not group of participants to influence the two obtain a set of scores in variables being each treatment condition. examined. 4 terminologies: ❖ Independent variable is the variable manipulated by the researcher. ❖ Treatment condition is a situation or environment characterized by one specific value of the manipulated variable. ❖ Levels are the different values of the independent variable selected to create and define the treatment conditions. ❖ Dependent variable is the variable that is observed for changes to assess the effects of manipulating the independent variable. ❖ Extraneous variables are all variables in the study other than the independent and dependent variables. 5 Causation & the Third-Variable Problem ❖ One problem for experimental research is that variables rarely exist in isolation. ❖ Although, a study may establish that two variables are related, it does not necessarily mean that there is a direct (causal) relationship between the two variables. 6 Causation & the Directionality Problem ❖ Although a research study may establish a relationship between two variables, the existence of a relationship does not always explain the direction of the relationship. 7 Controlling Nature ❖ To establish a cause-and-effect relationship, an experiment must control nature, essentially creating an unnatural situation wherein the two variables being examined are isolated from the influence of other variables and wherein the exact character of a relationship can be seen clearly. 8  2. Distinguishing Elements of an Experiment 9 Manipulation ❖ consists of identifying the specific values of the independent variable to be examined and then creating a set of treatment conditions corresponding to the set of identified values. 10 Manipulation ❖ Manipulation and the Directionality Problem simply observing that a relationship exists does not explain the relationship and certainly does not identify the direction of the relationship. ❖ Manipulation and the Third-Variable Problem Manipulation is to help researchers control the influence of outside variables. However, the existence of a relationship does not necessarily mean that there is a direct connection between the two variables. 11 Control ❖ Control and the Third-Variable Problem The particular concern is to identify and control any third variable that changes systematically along with the independent variable and has the potential to influence the dependent variable. ❖ Extraneous Variables and Confounding Variables With thousands of potentially confounding variables, however, the problem of controlling (or even monitoring) every extraneous variable appears insurmountable. 12  3. Controlling Extraneous Variables 13 Control by Holding Constant or Matching ❖ Holding a Variable Constant By standardizing the environment and procedures, most environmental variables can be held constant. Holding a variable constant eliminates its potential to become a confounding variable. ❖ Matching Values across Treatment Conditions Control over an extraneous variable can also be exercised by matching the levels of the variable across treatment conditions. 14 Control by Randomization Randomization is the use of a random process to help avoid a systematic relationship between two variables. Random assignment is the use of a random process to assign participants to treatment conditions. 15 Comparing Methods of Control ❖ The goal of an experiment is to show that the scores obtained in one treatment condition are consistently different from the scores in another treatment and that the differences are caused by the treatments. 16 Advantages & Disadvantages of Control Methods ❖ The two active methods of control (holding constant and matching) require some extra effort or extra measurement and, therefore, are typically used with only one or two specific variables identified as real threats for confounding. 17  4. Control Conditions & Manipulation Checks 18 Control Conditions ❖ experimental condition is the condition in which the treatment is administered ❖ control condition is the condition in which the treatment is not administered. 19 Control Conditions ❖ No-Treatment Control Conditions a condition in which the participants do not receive the treatment being evaluated. ❖ Placebo Control Conditions placebo is an inert or innocuous medication, a fake medical treatment that, by itself, has absolutely no medicinal effect, but produces a positive or helpful effect simply because an individual expects or believes it will happen. placebo effect refers to a positive response by a participant to an inert medication that has no real effect on the body. The placebo effect occurs simply because the individual thinks the medication is effective. placebo control condition is a condition in which participants receive a placebo instead of the actual treatment. 20 Manipulation Checks ❖ manipulation check is an additional measure to assess how the participants perceived and interpreted the manipulation and/or to assess the direct effect of the manipulation. ❖ It is particularly important in four situations: 1. Participant Manipulations. 2. Subtle Manipulations. 3. Placebo Controls. 4. Simulations. 21  4. Increasing External Validity: Simulation and Field Studies 22 ❖ Simulation the creation of conditions within an experiment that simulate or closely duplicate the natural environment in which the behaviors being examined would normally occur. ❖ Field Studies research conducted in a place that the participant or subject perceives as a natural environment. 23 Advantages and Disadvantages of Simulation and Field Studies ❖ Advantage: they allow researchers to investigate behavior in more lifelike situations and, therefore, should increase the chances that the experimental results accurately reflect natural events. ❖ Disadvantage: allowing nature to intrude on an experiment means that the researcher often loses some control over the situation and risks compromising the internal validity of the experiment. 24 Thanks ! Reference: Research Methods for the Behavioral Sciences, Sixth Edition Frederick J. Gravetter and Lori-Ann B. Forzano 25