Research Methods 

Psychology uses specific methods of behavioral research to standardize findings. The experimental method

has four parts: hypothesis, procedure, results, conclusions

Hypothesis: A possible explanation of events that is to be tested. In simple experiments, usually in an IF-THEN format.

IF statement is the Independent Variable. The factor that creates what you wish to study.

“If you wear celery on your head” (IV) THEN statement is the Dependent Variable. The changed condition created by the independent variable. According to your

hypo., It can only exist due to the independent variable.

“Then dogs will bark at you” (DV)

“If you wear celery on your head, then dogs will bark at you”- YOUR HYPOTHESIS

Procedure is the actual experiment itself. Care must be taken to avoid factors that may invalidate the results. These are called extraneous variables, and must be minimized.

Subjects are the people/animals that are used in the experiment. They are placed in two basic groups.

Experimental Group: They have the condition found in the independent variable (IV) Your hope is that they will change in the way found in the dependent variable (DV). Subjects in the experimental group would be those who wear celery on their head.

Control Group: They do not have the condition found in the IV. This group is used to compare with the Experimental group. Your hope is that they do not change in the way found in the DV.

Subjects in the control group would be those who do not wear celery on their head.

Who are your subjects? Sample: Selection of subjects from a larger population. Random Sampling: Sample in which each potential subject has equal

chance of being selected. Example: study pilot trainees, use alphabetical list and select every third name.

Representative Sampling: sample carefully chosen so that the

characteristics of the subjects correspond closely to the characteristics of the larger population. Example: studying the graduating class—250 girls and 300 boys. Your sample will be 25 girls and 30 boys to use proper representative sampling.

Biased Sampling: Sample that does not truly represent the whole

population.

M&M Experiment on sample size…

• Lets eat a tasty treat while learning the importance of sample size.

• Needed materials: – Packet page 28– Writing utensil – Calculator of some sort

Results are the raw information your procedure gave you. There are two basic qualities to experimental resultsReliability: This is the degree of consistency of your results. If you ran the experiment over, would you get the same results? *The more an experiment is run with the same results, the morereliable it is considered to be.

Validity: This is the degree of usefulness of your results. Did you results allow you to prove/disprove your hypothesis? *Validity is really dependent on the quality of procedure. A poorly

constructed/run experiment will have invalid results.

Conclusions are overall statements made by the researcher after the experiment relative to the original hypothesis.

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Everyone makes mistakes…

But let’s try to avoid it! Good experiments limit errors

whenever possible

Experimental Errors by Research

Experimenter Bias: Preconceived attitudes the researcher/tester

has that affect how they view the results.

– For example : A teacher doesn’t like you, so they grade your tests harsher

Experimental Errors by Research

Subject Bias: Preconceived attitudes the subject has affecting

the results.

For example: “I hate this teacher, so I won’t try to do well on this test”

Experimental Errors by Research

Demand Characteristics and Recording Errors: The unforeseen impact of something in the environment

Examples:A blinking light during a test bothers some takers. Group members talking and “giving away hypothesis”

Experimental Errors by Research

In general, any factor that lessens your reliability or validity is considered an Extraneous Variable. From large assumption problems like bias, or little glitches in the procedure.

Experimental Errors by Subjects

“oops!”

Halo Effect • The first traits we recognize

in people then influence the interpretation and perception of other traits • “Attractive people are

often judged as having a more desirable personality and more skills than someone of average appearance. Celebrities are used to endorse products that they have no expertise in evaluating.”

Hawthorne Effect • The feeling that you are being

studied or watched causes you to act different than in natural (relaxed) environment

John Henry Effect

• The ability of a sense of competitiveness to occur during an experiment causing a desire to “beat the other group”

• This causes the data to be invalid and unreliable

Novelty Effect • Experiments often have people trying

something new or interesting…therefore they may be more motivated than usual.

“Yippee! I can’t wait to try it!”

“This is the coolest thing ever!”

• Good luck planning your experiments! Avoid as many errors as possible