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
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 Disadvantage
May 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
questions
Advantages Disadvantages
Get 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 0
0.5 2 0
1.0 3 0
1.5 4 2
2.0 1 1
2.5 2 6
3.0 1 4
3.5 0 1
4.0 1 1
Total 15 15