Experimental design

Experimental research is used to demonstrate cause and effect relationships

  • Seeks to determine if one factor influences another

  • Involves controlling factors and situations

    Examples

  • Does being stared at increase feelings of anxiety and discomfort?

Advantages of experimental research

  • Allows cause an effect to be considered

  • Can be replicated by others

  • Researchers can control experimental situations

  • Greater potential for representing population

Disadvantages of experimental research

  • Can be difficult to design

  • Doesn’t always reflect realistic relationships

  • Human error may be present in design, execution, or reporting of result

A variable can be anything that can be measured within an experiment Such as

  • Emotion

  • Beliefs

  • Objects

  • Behaviors

The purpose of experimental research is to discover whether changes in one variable X will be changes in another variable Y. X would be considered the Independent variable and Y the dependent variable

Independent variable Is the research variable that is manipulated in an experiment to test its impact on another variable.

  • Hypothesized to have some effect on or influence on the dependent variable

Dependent variable Is the research variable that changes or varies as a result of the independent variable.

  • Hypothesis to be influenced by or dependent upon manipulations of the independent variable

There often is a variety of variables that can influence or interfere with the relationship between the independent and dependent variable Such as extraneous variables and confounding variables.

Extraneous variables Our variables that are not included in a specific study, but seem likely to influence the dependent variable

  • Variables that are unaccounted for can interfere with assessing the relationship between the independent and dependent variable.

Confounding variables are variables that interfere with study results because of a connection to the independent variable that is not easy to separate.

  • Cannot determine if effects on dependent variable are due to the independent variable or confounding variable

Using groups in experiments

  • Grooves are often used in experiments in order to compare a group receiving treatment to a group receiving no treatment.

  • Treatment group is the experiment group

  • Non-treatment group is the control group

Experimental group is a group of participants who receive treatment through the manipulation of the independent variable.

Control group in an experiment is a group of participants who do not receive the treatment that is given to the experimental group.

Group characteristics

Both experimental group and control group should be as identical as possible, except for the presence of treatment

Examples

  • If an experiment involves high school seniors then participants in both groups need to be high school seniors

  • If an experiment is to measure the effects of treatment on depression, then both groups need to contain individuals who are diagnosed with clinical depression

Group assignments

Random assignment occurs when participants are assigned to a group by chance meaning everyone has an equal chance at being either the experimental or control group and allows more Objectivity and participant selection.

Sample experimental design

Research question

  • What effect does the amount of times study have on exam scores?

Testable hypothesis

  • Students who study for at least one hour each night will achieve better scores than those who do not

    So the independent variable is time spent on studying and the dependent variable is the score on the exam.

Extraneous or confounding variables

  • Method of studying

  • Available materials

  • Location of study

  • Overall intelligence

  • Time of day

  • Study environment

Placebo, A substance or treatment having no actual effect that is administered as a control in experimental testing

  • participants assumed that the substance is an active agent used as a treatment

Experimental procedure variations

Single blind study is a study in which the researchers are aware of group assignments but participants remain unaware of what group they are assigned to.

Double blind study is a study in which neither the subjects nor the researchers are aware of the group that the subjects have been assigned to.

Generalizing research results

Generalizability is the degree to which the findings of a study may be applied to a large larger population. The Generalization factors

  • Sample representation

  • Sampling methods and sample size

  • Research timelines

    SAMPLE REPRESENTATION

    population is the group from which participants are taken.A sample is the group of participants included in the study that represents the target population. A Sample should represent the population equally and accurately in terms of ethnicity, gender incomeFamily size

SAMPLING METHODS

  • Random Sampling

    A method in which participants are selected by chance to participate in a research study. Increases generalizability

  • Quota sampling

    Is a method that includes only certain groups to ensure a fair or appropriate representation of those groups. Helps to avoid over sampling.

  • Convenience sampling

    is a sampling method in which participation is based on availability of participants are volunteers.

SAMPLING SIZE

Your sample size needs to be large enough to give you accurate results. If it’s too small, you can’t be confident that the results will be accurate.The larger sample size the more confidence you can have that your results can be generalized to the population.

RESEARCH TIMELINESS

Your study also has to be recent in order to be useful. You can’t use a study to generalize to people too far into the future or pass because there are too many variables you haven’t controlled for.