Research MethodsChapter 2

How Do Psychologists Develop New Knowledge?• Psychologists, like researchers in all other sciences, use the

scientific method to test their ideas empirically.

How Do Psychologists Develop New Knowledge?• Empirical investigation – “experienced based”

An approach to research that relies on sensory experience and observation as research data.

• Scientific method –A five-step process for empirical investigation of a hypothesis under conditions designed to control biases and subjective judgments.

• A main goal of psychological science is to develop scientific explanations for behavior and mental processes.

• We call these explanations, THEORIES!• To scientists theory means the power to explain the facts and its

ability to be tested objectively.

The Five Steps of the Scientific Method

• Developing a hypothesis• Performing a controlled test• Gathering objective data• Analyzing the results• Publishing, criticizing, and replicating the results

Developing a hypothesis• Hypothesis –

A statement predicting the outcome of a scientific study• Operational definitions –

Exact procedures used in establishing experimental conditions and measurement of results

Performing a controlled test• Independent variable –

The variable manipulated by the experimenter • Random presentation –• Using chance alone to determine the order in which the stimulus

is presented

Gathering objective data

• Data –Information gathered by researcher and used to test a hypothesis

• Dependent variable –The measured outcome of a study; the responses of participants in a study

Analyzing the results• Based on statistical analyses of results, the hypothesis is

accepted or rejected

Publishing, criticizing, and replicating the results• Researchers must find out whether their work can withstand

the scrutiny of the scientific community.• How is this done?

Psychological Research• What are confounding and extraneous variables? How do

they effect the scientific method?

• What is “random assignment” and how is it used in experiments?

Non-Experimental Methods• There are some situations in which experiments cannot be

done for ethical reasons. • Non-Experimental methods can yield useful data, but they are

just not “true” experiments because they are missing a component of the experiment, usually in the areas of the controls. • Ex Post Facto: subjects are chosen on the basis of a preexisting

condition. Example?

Types of Psychological Research

• In experiments, the researcher controls all the conditions and directly manipulates the conditions

• Non-experimental methods include:• Correlational studies• Surveys• Naturalistic observation• Longitudinal studies• Cross-sectional studies• Cohort-sequential studies

Correlation Studies• Are used to see a relationship (correlation) btw two variables.• Smoking and lung cancer.

• CORRELATION DOES NOT NECESSARILY MEAN CAUSATION!

Continued…• The degree of correlation is normally expressed as a number.

R= correlation coefficient• Range from negative # (-1.0: + 1.0)• If variables have no relationship= zero correlation• Relationship in which they vary in the same direction = positive

correlation (+0.4)• A correlation can show a strong relationship even when its

negative.

Surveys• Not a true experiment, but if conducted correctly can yield

useful data.• Researchers need to make sure the questions are not skewed or

bias.• Participants tend to not take surveys seriously, due to this surveys

tend to yield incorrect results.

Naturalistic Observation• Subjects are observed in their natural environment. • Subjects should NOT know they are being observed, this way

the behavior being observed is actual behavior in their natural state.• Children on the playground, animals in the wild.

Longitudinal Studies• One group of subjects is followed/observed for an extended

period of time. • Benefits: same subject group• Negatives: Time and expense

• Example: Following special needs children for their first 15 years of their lives.

Cross-Sectional Studies• Examines a representative cross section of the population and

tests/surveys these subjects at one specific time.• Will yield data similar to longitudinal studies, but the data won’t

be as accurate.

Cohort-Sequential Studies• Similar to Cross-Sectional• Here, researchers take a cross section of the population and

then follows each cohort or group for a short period of time.• This study takes less time than longitudinal studies and yields

more accurate data than a cross sectional study.

Sources of Bias• Bias could affect the way an experimenter designs a study,

collects data, or interprets results• Sources of bias include:• Personal bias• Expectancy bias

Personal Bias• Involves and individuals beliefs, preferences, assumptions, or

prejudices. • This bias can cause scientists to notice only evidence

confirming their hypotheses and to ignore contrary data

Expectancy Bias• This bias effects observations when observers expect and

LOOK for certain outcomes.

• Bias not only leads to erroneous conclusions, but it can also be expensive.

How to “control” a Bias• Double blind studies attempt to control bias.• This strategy ensures that the experimenters will not

inadvertently treat the experimental group differently from the control group, so that neither group will have any idea about the expected response.

• Placebo:• Researchers must also attempt to control confounding

variables

Ethics in Research• In order to make sure research is conducted in an appropriate

manner, guidelines are put in place by the APA, IRB, and IACUC.• These boards review and approve all research and make sure the

experiments comply with local, state, national requirements. • Deception • Debriefing• Animal research

Deception• Participants should be advised about what challenges they will

face and give them an opportunity to drop out.• In other situations, participations must be informed of

deception as soon as possible with out compromising the study's research goals.

• They must be debriefed to make sure there is not lasting ill effects.

Animal Studies• Psychologists, most support the use of animal research. But,

they do not support or approve of animal studies that cause harm, pain, or result in death of their subjects.

Questions Science Cannot Answer

• The scientific method is not appropriate for answering questions that cannot be put to an objective, empirical test• Ethics• Morality• Religious beliefs• Preferences

How Do We Make Sense of the Data?

• Researchers use statistics for two major purposes:(1) descriptively to characterize measurements made on groups or individuals and(2) inferentially to judge whether these measurements are the result of chance