Psychological Research & StatisticsChapter 20

Objectives Describe the process of psychological

research Name the different types of psychological

research and some of the methodological hazards of doing research

Describe descriptive & inferential statistics Name specific research methods used to

organize data

Key terms Case study Central tendency Control group Correlation Correlation

coefficient Cross-sectional

studies Dependent

variable Descriptive

statistics Experimental

group

Frequency distribution

Histogram Independent

Variable Inferential

statistics Longitude studies Mean Median Mode Naturalistic

observation Normal curve

Population Range Sample Self-fulfilling

prophecy Standard

deviation Statistics Survey Validity Variable Variance

APA CODE of ETHICS1. Informed Consent2. Protect subjects from harm

1. Psychological 2. Physical

3. Subjects can withdraw anytime4. Debriefing5. Subjects anonymous

What do you think? Amazing Randi

Gathering Data How do psychologist collect information

about the topic they’ve chosen to study?

Social psychologist who is studying the effects of group pressure is likely to conduct an experiment

A psychologist who is interested in personality theories might begin with intensive case studies of individuals

Whatever the approach, decision must be made in advance

Gathering Data: VALIDITY Stop hair loss

“Freedom from wrinkles”

Huge weight lose in “just 2 weeks!”

Self-help books: (How to achieve the perfect relationship)

Actors playing experts

Task of psychologists is to determine validity: Validity: The ability of a test to measure what it is

intended to measure; verifying a theory A theory cannot be accepted until it has been repeatedly tested

Gathering Data: SAMPLES A psychologists wants to know how the desire

to get into college affects the attitudes of high-school juniors and seniors. Would it be possible to test all in the country? What would the psychologist do?

Sample: The small portion of data, out of the total amount available, that a researcher collects

Population: The total group of subjects from which a sample is drawn

Gathering Data: SAMPLES Choosing a sample may be tough!

Samples must be representative of the population a researcher is studying

Ex: If you wanted to know how tall American men are, what professional group would you make certain not to have a disproportionately large number of representatives?

NBA basketball players

If you didn’t what would this sample be? Biased, it would not represent American men in

general

Gathering Data: SAMPLES How to avoid a biased sample?

Take a purely random sample To ensure that each individual within the scope of the

research has an equal chance of being represented How?

Choose every 20th name on school enrollment lists

Deliberately pick individuals who represent the various subgroups in the population being studied

How? Research on students, select students of both sexes,

varying ages, of all social classes, from all neighborhoods (Stratified sample)

Gathering Data: CORRELATIONS & EXPLANATIONS Examine a relationship between two

sets of observations EX: Students grades & number of hours

they sleep

Correlation: The degree of relatedness between two sets of data

Gathering Data: CORRELATIONS & EXPLANATIONS What would be the correlation between IQ scores

and academic success? High IQ tend to go with high grades Low IQ tend to go with low grades

Negative correlation Smoking cigarettes and living long, healthy life

Student example of correlations?

Experiments Why would a researcher choose

experimentation over other research methods? Experimentation enables the investigator

to control the situation and to decrease the possibility that unnoticed, outside factors will influence the results

What is an experiment designed to do? Prove or disprove a hypothesis

Experiments Variables: In an experimental situation,

any factor that is capable of change

2 types of variables Independent: In an experiment, the factor

that is deliberately manipulated by the experimenters to test its effect on another factor; the cause of change

Dependent: The factor, chosen by the experimenter, that may or may not change when the independent variable is changed

Experimental Method Worksheet

Independent & Dependent variable

Experiments Experimental group: The group of

subjects to which an independent variable is applied

Is there a chance that subjects will act differently because it is an experiment?

Controlled group: Group who is treated in the same way as the experimental group, except the experimental treatment (independent variable) is not applied

Experiments What is necessary in all experiments?

Control group

What would happen without a control group? Researcher cannot be sure the

experimental group is reacting to- a change in the independent variable

Worksheet Thinking Drunk, Driving Drunk

Marriage: Practice Makes Imperfect

Naturalistic Observation Researchers need to understand the

way people & animals behave naturally.

Naturalistic observation: Studying phenomena as they occur in natural surroundings, without interfering

Naturalistic Observation Examples

Psychologists might join a commune Take position behind a 2-way mirror to watch

youngsters play Live in the jungle to study behavior of gorillas

(Gorillas in the Mist)

CARDINAL RULE of Naturalistic Observation: Avoid disturbing the people or animals you are

studying

Walk on the Wild Side! This is the way we walk

Case Studies Case study: An intensive

investigation of an individual or group, usually focusing on a single psychological phenomenon

Value of case studies? Provide a wealth of descriptive material

that may generate new hypotheses that researchers can then test under controlled conditions with comparison groups

New York University Investigate the psychological

characteristics of people receiving death

15 inmates

Are death row inmates shrewd, cold killers?

New York University Findings

All 15 had history of severe head injury 12/15 showed signs of brain damage Most are below average IQ

Surveys Survey: Sampling of data, obtained

through interviews and questionnaires

May be impersonal, but most practical way to gather data on the attitudes, beliefs, and experiences of large numbers of people

Surveys

Advantages DisadvantageMay gather a lot of information on the attitudes, beliefs, and experiences of large numbers of people

ImpersonalWho responds?Wording of questionsLow response rate90% of people surveyed said…

Interviews Studying people face to face and asking

questionsAdvantages DisadvantagesGet detailed personal information

Interviewer biasInterviewees fact from fiction

Longitudinal Studies Longitudinal Studies: Repeatedly

gathering data on the same group of subjects over a period of time for the purpose of studying consistencies and changes

Has behavior or feelings changed?

Cross-sectional Studies Alternative approach to gathering data is

Cross-sectional study: Acquiring comparable data subgroups on the basis of certain criteria for the purpose of studying similarities and differences

Ex: Give an IQ test to individuals 30,40, & 60 years old and compare average scores, then draw conclusions about intelligence at various ages

Cross-sectional Studies Advantages:

Less expensive Reduce amount of time needed for study

Disadvantage With the previous example with IQ and age

Example concluded that intelligence declines with age, but age may not be the primary cause of decline

What could have influenced the results? Education, life experiences, opportunity

Avoiding Errors in doing Research

Self-fulfilling prophecy: A belief, prediction, or expectation that operates to bring about its own fulfillment

How to avoid self-fulfilling prophecy is to use the double-blind technique

Avoiding Errors in doing Research

Single-blind technique Wants to study the effects of a tranquilizer One group receives the drug Other group receives a placebo (harmless substitute for

the drug)

Which group is experimental & controlled?

Next step to compare performances on a series of tests

Who is blind in this experiment?

Avoiding Errors in doing Research

How could we make the previous experiment a double-blind experiment? Both the researcher and the subjects do

not know who took the drugs or the placebo

Eliminates the possibility that the researcher will unconsciously find what she expects to find about the effects of the drug

Avoiding Errors in doing Research

Psychologists are like you and I, they have attitudes, feelings, and ideas of their own, and their reactions to different subjects may distort the results of a study.

Researchers may unknowingly react differently to male and female subjects, short and tall subjects, subjects who speak with an accent

Avoiding Errors in doing Research

What would happen if several children being studied in a play area were introduced to a television camera man and said they were going to be on TV tonight?

Statistical Evaluation How many times have you been told

that, in order to get good grades, you have to study? A psychology student named Jolly Mames has always restricted the amount of TV she watches during the week, particularly before a test. She has a friend though who does not watch TV before a test but who still does not get good grades. This fact challenges Jolly’s belief.

Statistical Evaluation Jolly hypothesizes that, among her

classmates, those who watch less TV get better grades, she decides to conduct a survey to test the validity of her hypothesis.

Asks 15 students in her class to write down how many hours of TV they watch the night before their weekly psychology quiz and how many hours they watched on the night after the quiz.

Statistical Evaluation Jolly collect addition information like

checking off familiar products on a list of20 brand name items that were advertised on TV the night before the quiz. Jolly also asks her subjects to give their height

Data is turned in and Jolly is overwhelmed with the amount of information she has collected

Statistical Evaluation How can it be organized so it will make sense?

How can Jolly analyze it to see whether it supports or contradicts her hypothesis?

Statistics: The branch of mathematics concerned with summarizing and making meaningful inferences from collections of data

Before After Grade (10 highest possible) Products

Height

0.0 1.5 5 2 71

0.5 2.5 10 4 64

0.5 2.5 9 6 69

1.0 2.0 10 14 60

1.0 2.5 8 10 71

1.0 1.5 7 9 63

1.5 3.0 9 7 70

1.5 2.5 8 12 59

1.5 2.5 8 9 75

1.5 3.0 6 14 60

2.0 3.0 5 13 68

2.5 2.5 3 17 65

2.5 3.5 4 10 72

3.0 3.0 0 18 62

4.0 4.0 4 20 67

Statistical EvaluationHow much television did the two students with the best grades watch the night before the quiz?

Before After Grade (10 highest possible) Products

Height

0.0 1.5 5 2 71

0.5 2.5 10 4 64

0.5 2.5 9 6 69

1.0 2.0 10 14 60

1.0 2.5 8 10 71

1.0 1.5 7 9 63

1.5 3.0 9 7 70

1.5 2.5 8 12 59

1.5 2.5 8 9 75

1.5 3.0 6 14 60

2.0 3.0 5 13 68

2.5 2.5 3 17 65

2.5 3.5 4 10 72

3.0 3.0 0 18 62

4.0 4.0 4 20 67

Descriptive Statistics When the study is complete, the first task is to

organize the data in as brief and clear a manner as possible.

Jolly must put her responses together in a logical format. When she does she will be using

Descriptive statistics: The listing and summarizing of data in a practical, efficient way, such as graphs and averages

Descriptive Statistics Distributions of data:

One of the 1st steps is to organize their data is to create frequency tables and graphs.

Tables and graphs provide a rough picture of the data (initial peek of data) Are scores bunched up or spread out? What scores occur most often?

Descriptive Statistics Jolly is interest in how many hours of TV her subjects

watched the night before and the night after the quiz.

Jolly uses the numbers of hours of TV viewing as categories and then she counts how many subjects reported each category of hours before and after the quiz.

Jolly has created a table Frequency distribution: An arrangement of data

that indicates how often a particular score or observation occurs

Jolly’s Frequency TableHours Frequency

BeforeFrequency After

0.0 1 00.5 2 01.0 3 01.5 4 22.0 1 12.5 2 63.0 1 43.5 0 14.0 1 1Total 15 15

Quiz: Understanding Research Video