copyright © allyn & bacon 2007 chapter 2: research methods

Copyright © Allyn & Bacon 2007

Chapter 2:Chapter 2:

Research MethodsResearch Methods


How Do Psychologists How Do Psychologists Develop New Knowledge?Develop New Knowledge?

Psychologists, like researchers in all other

sciences, use the scientific method to test their ideas

empirically.


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

How Do Psychologists How Do Psychologists Develop New Knowledge?Develop New Knowledge?

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


The Five Steps of the Scientific MethodThe Five Steps of the Scientific Method

Developing a hypothesisDeveloping a hypothesis

Performing a controlled testPerforming a controlled test

Gathering objective dataGathering objective data

Analyzing the resultsAnalyzing the results

Publishing, criticizing, and Publishing, criticizing, and replicating the resultsreplicating the results


Developing a Developing a hypothesishypothesis

Performing a controlled test

Gathering objective data

Analyzing the results

Publishing, criticizing, and replicating the

results

Hypothesis –A statement predicting the outcome of a scientific study.

Operational definitions –Exact procedures used in establishing experimental conditions and measurement of results.



Operational DefinitionOperational Definition

• A definition that specifies the operations used to produce or measure something; a way to give it a numerical value.

• Example of an operational definition:

Televised violence = the # of acts shown or described in which one person injures another.


Developing a hypothesis

Performing a Performing a controlled testcontrolled test




results

Independent variable –The variable manipulated by the experimenter.

Random presentation –Using chance alone to determine the order in which the stimulus is presented.





Gathering Gathering objective dataobjective data



results

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 Analyzing the resultsresults


results

Based on statistical analyses of results, the hypothesis is accepted or rejected.







Publishing, Publishing, criticizing, and criticizing, and replicating the replicating the

resultsresults


Researchers must find out whether their work can withstand the scrutiny of the scientific community.


Types of Psychological ResearchTypes 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


Sources of BiasSources of Bias

-Sources of bias include:• Personal bias• Expectancy bias

-Bias could affect the way an experimenter designs a study, collects data, or interprets results.

-Double blind studies attempt to control bias.

-Researchers must also attempt to control confounding variables.


Ethics in ResearchEthics in Research

APA – American Psychological Association

IRB – Institutional Review Board

IACUC – Animal research (must be Appropriate, Beneficial, and Caring)

• Deception

• Debriefing


Questions Science Cannot AnswerQuestions Science Cannot Answer

• The scientific method is not appropriate for answering questions that cannot be put to an objective, empirical test:

• Ethics

• Religious beliefs

• Values

Milgram Experiment

Shock GeneratorCaution

Amps

On

Intensity Resistance

Amp Meter

SlightShock

ModerateShock

StrongShock

VeryStrongShock

IntenseShock

ExtremeShock

Danger XXXXXX

Milgram ExperimentMilgram Experiment

Two thirds of participants delivered the maximum 450 volts to the learner!

Statistical EvaluationStatistical Evaluation


Descriptive Statistics:

Statistical procedures used to describe characteristics and responses of groups of subjects.

Mathematical summaries of results.


Frequency distribution:A summary chart,

showing how frequently each of the various scores in a set of data occurs.

Rank Degree of agreement Number

1 Strongly agree 25

2 Agree somewhat 35

3 Not sure 20

4 Disagree somewhat 15

5 Strongly disagree 5


Histogram: A bar graph depicting

a frequency distribution.

The height of the bars indicates the frequency of a group of scores.

Measures of Central TendencyMeasures of Central Tendency

AVERAGES

1. Mean

2. Median

3. Mode


Mean:Most commonly used to describe a set of data.

Calculated by adding all the scores and dividing by the total number of scores.

*What is the mean of the following numbers?

2, 4, 8, 9, 7, 3, 9

Answer:Answer:

6


Median:The middle score in a list of

scores arranged from highest to lowest.

*What is the median in this number list?

2, 3, 5, 7, 9Answer: 5

Find the median:11, 6, 9, 12, 4, 7,

2, 5

AnswerAnswer::

6.5


Mode:The score that occurs the most frequently.

*What is the mode of this distribution?

2, 3, 4, 6, 6, 7, 9

Answer:Answer:

6


What happens if there is more than mode???

Example:

2, 3, 4, 4, 5, 6, 7, 7, 8, 9


The distribution is called BIMODAL.

2 modes = bimodal

What is the mode?

2, 3, 4, 4, 5, 6, 7, 7, 8, 9

ANSWER:

4 AND 7

Measures of VariationMeasures of Variation

Variance:A measure of

difference or spread

(high or low).

Range:Subtract the lowest score in the data set from the highest score and add 1.

*If the highest quiz grade was 12 and the lowest quiz grade was 0, what is the range?

Answer:Answer:

13

Sampling

SamplingSampling

Random sample:A sample group of subjects

selected by chance (without bias).

Representative sample:A sample that reflects the

distribution of important variables in the larger population in which the researchers are interested.

CorrelationCorrelation::

The measure of a relationship between two variables.

Correlation Coefficient:A mathematical estimate of the relationship

between two variables.-1.0 to +1.0

0 = No Relationship


POSITIVE CORRELATION: +As one variable increases, the second variable

increases.

Example???

NEGATIVE CORRELATION: -As one variable increases, the second variable

decreases.

Example???

Participant Income

Years of Education

#1 125,000 19

#2 100,000 20

#3 40,000 16

#4 35,000 16

#5 41,000 18

#6 29,000 12

#7 35,000 14

#8 24,000 12

#9 50,000 16

#10 60,000 17

Participant GPA

TV (hours per week)

#1 3.1 14

#2 2.4 10

#3 2.0 20

#4 3.8 7

#5 2.2 25

#6 3.4 9

#7 2.9 15

#8 3.2 13

#9 3.7 4

#10 3.5 21

CorrelationsCorrelations

Imagine reading four correlational studies with the following scores:

-.3 -.8 .4 .7

Which study has the strongest results?

CorrelationsCorrelations

-.8

is the strongest correlation

(The negative sign means that its direction is

negative)


Normal distribution:A symmetrical frequency of scores clustered

around the mean.

Bell-shaped curve


Standard Deviations:A measure of variability that describes an

average distance of every score from the mean.


Inferential statistics:Used to assess

whether the results of a study are reliable or whether they might be simply the result of chance.

Statistical SignificanceStatistical Significance

p<.05The probability that randomly generated results

would resemble the observed results is less than 5%

* The smaller the p value, the more impressive the results!


Statistically significant:Unlikely that the effects have arisen by

chance.

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