The Experiment

• Only research method capable of showing cause and effect

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Experimental Research

• Explores cause and effect relationships.

Eating too many bananas causes Aggressive behavior

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Steps in Designing an Experiment

1. Question2. State Hypothesis3. Pick Population: Random Selection then

Random Assignment.4. Operationalize the Variables5. Identify Independent and Dependent

Variables.6. Look for Extraneous Variables7. Type of Experiment: Blind, Double Blind

etc..8. Gather Data9. Analyze Results

Hypothesis• A statement about the relationship between two or

more variables• Must be testable and refutable• Instead of proving the hypothesis, science usually

tries to disprove a null hypothesis.

Null Hypothesis (H0): opposite of hypothesis

Hypothesis Example:

H1: Gender has an effect on spatial ability

H0: Gender does not have an effect on spatial ability

Population – The larger group of people from which a sample is drawn

Sample: Representative of the population

Two ways to get sample

Random: Every member of the pop has = chance

Stratified: Sample is put together by picking a

group statistically equal to the population

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Assigning participants to experimental and control conditions by random assignment minimizes pre-existing

differences between the two groups.

Random Assignment

Variables• Independent Variable (I.V.): manipulated

by experimenter

• Dependent Variable (D.V.): MEASURED variable influenced by independent

• Operational definition

• Confounding/extraneous variables

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An Independent Variable is a factor manipulated by the experimenter. The effect of the independent variable is the

focus of the study. For example, when examining the effects of

breast feeding upon intelligence, breast feeding is the independent variable.

Independent Variable

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A Dependent Variable is a factor that may change in response to an independent variable. In psychology, it is usually a

behavior or a mental process.

For example, in our study on the effect of breast feeding upon intelligence,

intelligence is the dependent variable.

Dependent Variable

Control Measures

• Single-Blind: subject unaware of assignment

• Double-Blind: subject and experimenter unaware of placement

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Experimental Vocabulary• Independent Variable: factor that is

manipulated• Dependent Variable: factor that is

measured• Extraneous Variables: factors that

effect DV, that are not IV.• Experimental Group: Group exposed

to IV• Control Group: Group not exposed to IV• Placebo: inert substance that is in place

of IV in Control Group

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Analyze Results

• Use measures of central tendency (mean, median and mode).

• Use measures of variation (range and standard deviation).

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ExperimentationA summary of steps during experimentation.

Flaws in Research

• Sampling Bias

• Overgeneralization

• Placebo effect

• Hawthorne/Barnum effect

• Demand Characteristics

• Experimenter Bias

APA Ethical Guidelines for Human Research

All research goes before an institution review board (IRB) for approvalResearch involving humans must meet the following standards:

1. Informed Consent-participants must know that they are involved in research and give their consent or permission

2. Deception-if the participants are deceived in any way about the nature of the study the participants must be debriefed after the study is over

3. Coercion-participants cannot be coerced in any way to participate in the study.

4. Anonymity/Confidentiality -the identities and actions of participants must not be revealed in anyway by the researcher.

5. Risk -participants cannot be placed at significant mental or physical risk. DO NO HARM

6. Debriefing Procedures-participants must be told of the purpose of the study and provided with ways to contact the researchers about the results after the study is complete

 

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Ethics in Research with Animals

1. (Purpose) They must have a clear scientific purpose. The research

must answer a specific, important scientific question. Animals are chosen because they are best-suited to answer the question at hand.

2. (Care) They must care for and house animals in a humane way.

3. (Acquiring animals) They must acquire animal subjects legally.

Animals must be purchased from accredited companies. If wild

Animals must be used, they need to be trapped in a humane way.

4. (Suffering aka DO NO HARM) They must design experimental procedures that employ the least amount of suffering feasible.

5. (Supervision) A trained psychologist must supervise all research with

animals