PSYCHOLOGICAL RESEARCH. Population & Sample All research is aimed towards a particular population –The larger group that the results should apply to The

PSYCHOLOGICAL RESEARCH

Population & Sample

• All research is aimed towards a particular population– The larger group that the results should apply

to

• The people you actually study are called your sample– The sample MUST reflect the larger population!

Random Sample

• Sample should be random!– Best representation– Low bias

• Both on your part and/or your subject’s part!

• A sample is random if everyone in your population has an equal chance at being selected

• How can you ensure random sampling?

Observation Methods

Experimental ResearchExperimental ResearchExperimental ResearchExperimental Research

There are 5 major methods used to collect data in psychological

research:

Case StudiesCase StudiesCase StudiesCase Studies

SurveysSurveysSurveysSurveys

Correlational ResearchCorrelational ResearchCorrelational ResearchCorrelational Research

Naturalistic Naturalistic ObservationsObservationsNaturalistic Naturalistic

ObservationsObservations

Observation Methods


Involve the direct manipulation of one factor to better determine its effect

Advantages• allows cause-effect conclusions• control of extraneous variables

Disadvantages• artificial situations may not

represent natural events• lack of generalizability

Observation Methods

Independent Variable: Variable the experimenter is manipulating (has control over)

Dependent Variable: Variable the experimenter is measure (no control over)


EXAMPLE

• Dr. Duco wants to examine whether a new drug increases the maze running performance of older rats. Just like aging humans, older rats show signs of poorer memory for new things. Dr. Duco teaches two groups of older rats to find a piece of tasty rat chow in the maze. One group of rats is given the new drug while they are learning the maze. The second group is not given the drug. One week after having learned the maze he retests the rats and records how long it takes them to find the rat chow.

• Independent Variable?

• Dependent Variable?

A researcher wanted to study the effects of sleep deprivation on physical coordination. The researcher selected 25 year-old male college students and deprived some of the subjects to either 24, 36, or 45 hours of sleep.

Independent Variable?

Dependent Variable?

EXAMPLE

• Extraneous Variables: any other factor that might affect the dependent variable that the experimenter did not account for.


EXAMPLE

• A researcher wanted to assess whether mood influenced people's memory. The researcher hypothesized that positive moods would lead to greater memory performance than would a negative mood state. On Monday the researcher had 50 subjects learn a list of nonsense syllables and then watch a very humorous comedy film. Their recall of the list of syllables was then assessed. On Tuesday the researcher had a second group of 50 subjects learn the same list of nonsense syllables and then watch an upsetting documentary on World War II. Their recall of the list was then assessed after having watched the film.

• Extraneous Variables?

EXAMPLE

• A researcher wanted to see whether a new way of teaching English was superior to a more traditional approach. The researcher selected two Thursday night classes at a local community college. In one class the instructor used a traditional method, the second instructor used the newer approach. The researcher then assessed students language ability after they had completed the program.

• Extraneous Variable?

• Control Group: Serves as the baseline.

Untreated or unexposed to some procedure and then compared with treated subjects in order to validate the results (not manipulated)

• Experimental Group: contains the treated subjects in the experiment

(manipulated)


EXAMPLE

• I believe orbitz gum helps people quit smoking

What two groups would I form for my experiment?

Independent Variable? Dependent? Extraneous?

Observation MethodsNaturalistic Naturalistic

ObservationsObservationsNaturalistic Naturalistic

ObservationsObservationsInvolve observing behavior as it unfolds in a natural settingAdvantages

• behaviors are spontaneous/natural• inexpensive

Disadvantages• observer bias & selective attention• time consuming• Hawthorne effect

Observation Methods

Case StudiesCase StudiesCase StudiesCase Studies

Involve intensive examination of a single person or group

Advantages• deep understanding of subject• allows studies of rare behaviors

Disadvantages• difficult to generalize—conclusions may only apply to that particular person or group

Observation Methods

SurveysSurveysSurveysSurveys

Involve asking people questions about their beliefs and behaviors

Advantages• allows study of difficult-to-

observe behaviors, thoughts and feelings

• easy to distribute to large groupsDisadvantages

• people who respond may not be representative (volunteer bias)• responses may be biased or untruthful

Ways to Observe Change Over TimeLongitudinalLongitudinal

(p. 309)(p. 309)LongitudinalLongitudinal

(p. 309)(p. 309)

Observe one group of participants over an extended period of time

Advantages• enables researchers to see how individuals change over time

Disadvantages• time-consuming & expensive• risk of drop-outs

Ways to Observe Change Over Time

Cross-SectionalCross-Sectional(p. 309)(p. 309)

Cross-SectionalCross-Sectional(p. 309)(p. 309)

Compares people in different age groups all at one time

Advantages• less time-consuming

Disadvantages• differences may not be due to age or development, but due to other factors such as era

All Methods Work to Help Determine…

CorrelationCorrelation the extent to which two or more variables are associated with one another.

If two variables are highly correlated, it means that in the presence of one variable, there is a high likelihood that theother variable will also be present.

Correlation = Causation?

So…If two variables are highly correlated can we determine a cause-

and-effect relationship between them?

Variable A: poor attendance

Variable B: poor grades

Correlation

Variable A could cause variable B.

Poor attendance could cause people to miss tests and homework, and so they end up getting bad grades.

Correlation

Variable B could cause variable A.

The frustrations of poor grades might cause people to decide not to go to school.

CorrelationOr a third variable could cause A and B.

A person might have a full-time job that causes them to miss school and not do their homework.

Correlation vs. Causation

Violence

&

Ice Cream Sales

Or is there a 3rd Variable?

Correlation vs. Causation

• It’s important to remember that correlation does NOT equal causation!

• Always question the initial conclusion research might lead you to believe!

“Floss more, live longer”

“Lack of church attendance common denominator in families with ADHD kids.”

Correlation Causation

The only way to determine a cause-and-effect relationship is to carry out a

laboratory experiment!

The variables are controlled in these experiments

Documents

PSYCHOLOGICAL RESEARCH. Population & Sample All research is aimed towards a particular population –The larger group that the results should apply to The