EXDE Exam 2

Experiment

a type of study designed specifically to answer the question of whether there is a causal relationship between two variables

independent variable

variable the experimenter manipulates

presumed cause

Dependent variable

variable experimenter measures

presumed effects

Conditions

different levels of the independent variable to which participants are assigned

Control

holding extraneous variables constant in order to separate the effect of the independent variable from effect of extraneous variables

Extraneous variables

any variable other than the dependent and independent variable

Manipulate

changing the level, or condition, of independent variable systematically so that different groups of participants are exposed to different levels at different times

must involve active intervention of researcher

Single factor two-level design

• experiment design involving a single independent variable with two conditions

  • one witness to a condition in which there were five witnesses

• Variable: Speed

• Conditions: low or high speed

• only detects linear relationship

• between subjects- 2 separate groups, manipulated/subject IV

  • 2 matched groups, manipulated IV

• within-subjects (repeated measures)

  • 1 group, manipulated IV

Single factor multi-level design

• when an experiment has one independent variable that is manipulated to produce more than two conditions

• Manipulating the independent variable to produce three conditions

  • One witness, two witnesses, five witnesses

• EX: textile company wants to see how different percentages of cotton in fiber blend affect the tensile strength of fabric

  • percent of cotton measured at four different levels

Confounding variable

extraneous variable that varies systematically with the independent variable and thus confuses the effect of the independent variable with the effect of the extraneous one

participants IQ level

Treatment

any intervention meant to change people’s behavior for the better

Treatment condition

condition in which participants receive the treatment

Control condition

condition in which participants do not receive treatment

Randomized clinical trial

experiment that researches the effectiveness of psychotherapies and medical treatments

EX: 92 people with depression assigned to either group receiving therapy and medication vs group just receiving medication

No-treatment control condition

condition in which participants receive no treatment whatsoever

placebo effects

Placebo

simulated treatment that lacks any active ingredient or element that is hypothesized to make the treatment effective, but is otherwise identical to the treatment

Placebo effect

effect due to placebo rather than treatment

Placebo control condition

participants receive a placebo rather than treatment

Wait-list control condition

condition in which participants are told that they will receive treatment but must wait until participants in treatment condition have already received it

Between-subjects experiment

experiment in which each participant is tested in only one condition

important for different groups to be similar to each other

Random assignment

using a random process to decide which participants are tested in which conditions

Should meet two criteria: 50% chance of being assigned to each of two conditions and each participant is assigned to a condition independently of other participants

coin flip

Block randomization

all conditions occur once in the sequence before any of them is repeated

keeps number of participants in each group as similar as possible

123, 132, 231

Matched-groups design

experiment design in which participants in the various conditions are matches of the dependent variable or some extraneous variable(s) prior the manipulation of independent variable

rank-order PTs according to health prior to intervention or assignment, two healthiest PTs assigned to complete different conditions

Within-subjects experiment

each participant is tested under all conditions

PT asked to take 10mg of medicine, same PT comes back and asked to take 15mg of medicine

provides maximum control over extraneous PT variables

Order effect

occurs when participants’ responses in various conditions are affected by the order of conditions to which they were exposed

Disadvantage of within-subjects designs

Includes: carryover effect

Carryover effect

effect of being tested in one condition on participants’ behavior in later conditions

Type of order effect

Includes: practice effect and fatigue effect

Practice effect

effect where participants perform a task better in later conditions because they have had a chance to practice it

Type of carryover effect

Fatigue effect

effect where participants perform a task worse in later conditions because they become tired or bored

Type of carryover effect

Context effect (contrast effect)

unintended influences on respondents’ answers because they are not related to the content of the item but to the context in which the item appears

Counterbalancing

varying the order of the conditions in which participants are tested, to help solve the problem of order effects in within-subjects experiments

Complete counterbalancing

method in which an equal number of participants complete each possible order of conditions

In within-subject experiments, PTs complete conditions in different orders

Random counterbalancing

method in which the order of conditions is randomly determined for each participant

every possible order of conditions is determined and assigned to PT

Four Big Validities

internal, external, construct, statistical validity

Internal validity

refers to degree in which we can confidently infer a causal relationship between variables

external validity

refers to degree to which we can generalize the findings to other circumstances or settings, like real-world environment

Experiments sometimes have high external validity

Mundane realism

when participants and the situation studied are similar to those that the researchers want to generalize to and participants encounter every day

Psychological realism

where the same mental process is used in both lab and real world

construct validity

research question is clearly operationalized by the study’s methods

Operationalization

specification of exactly how the research question will be studied in the experiment design

Statistical validity

proper statistical treatment of data and soundness of researchers’ statistical conclusions

Proper use of tests

T-tests, ANOVA, regression, correlation

Subject pool

established group of people who have agreed to be contacted about participating in research studies

Research volunteers

more interested in topic, more educated, greater need for approval, higher IQ, more sociable, higher in social class

Experimenter expectancy effect

when the experimenter’s expectations about how participants “should” behave in the experiment affect how the participants behave

Standardization helps

Double-blind study

method to reduce experimenter bias, where neither participant nor experimenter is knowledgeable about the condition to which the participant is assigned

Manipulation check

• verifying experimental manipulation worked by using a different measure of the construct the researcher is trying to manipulate

• confirms independent variable is successfully manipulated

• EX: researchers trying to manipulate participants’ stress levels might give paper-and-pencil stress questionnaire or take blood pressure to verify procedure is successfully manipulated

• usually done at end of procedure, useful when results are null

Pilot test

small-scale study conducted to make sure that a new procedure works as planned

Key Takeaways from Ch. 5

• Experiment is type of empirical study that features the manipulation of an independent variable, measurement of dependent variable, and control of extraneous variables

• An extraneous variable is any variable other than the independent and dependent variables. A confound is an extraneous variable that varies systematically with the independent variable

• Experiments can be conducted using either between-subjects or within-subjects designs.

• Random assignment to conditions in between-subjects experiments or counterbalancing of orders of conditions in within-subjects experiments is a fundamental element of experimental research. The purpose of these techniques is to control extraneous variables so that they do not become confounding variables

• It is important to standardize experimental procedures to minimize extraneous variables, including experimenter expectancy effects

• Important to conduct one or more small-scale pilot tests of an experiment to be sure that the procedure works as planned

Non-experimental research

research that lacks the manipulation of an independent variable

• Single variable: how accurate are people’s first impressions? 

• Non-causal statistical relationship between variables: correlation between verbal intelligence and mathematical intelligence? 

• Participants can’t be randomly assigned: does damage to a person’s hippocampus impair the formation of long-term memory traces? 

• Broad and exploratory: what it’s like to be a working mother diagnosed with depression?

goal of research is to describe or predict

correlational or observational research

Correlational research

• research that is non-experimental because it focuses on the statistical relationship between two variables but does not include the manipulation of an independent variable

• no control to extraneous variables

• students’ self-esteem and GPA

• Why use? no causal relationships, can’t manipulate independent variable, establishes reliability and variability of measures

• higher in external validity than experimental research, lower internal validity

• describes and predicts

• provides converging evidence for theory

Observational research

research that is non-experimental because it focuses on recording systemic observations of behavior in a natural or lab setting without manipulating anything

Milgrim’s original obedience study

describes variables

naturalistic, participant, structured, case studies, archival

Cross-sectional studies

involve comparing two or more pre-existing groups of people (children at different stages of development)

Cohort effect

differences between the groups may reflect the generation that people come from rather than a direct effect of age

ADD!!!

Longitudinal studies

studies in which one group of people are followed over time as they age

effects of aging

Cross-sequential studies

studies in which researchers follow people in different age groups in a smaller period of time

combined elements of both cross-sectional and longitudinal studies

follow different age groups over time

ADD!!!

Study change over time

cross-sectional, longitudinal, or cross-sequential

Survey research

quantitative and qualitative method with two important characteristics; variables are measured using self-reports and considerable attention is paid to the issue of sampling

Respondents

participants in a survey or study

Cognitive processes involved in responding to survey item

Question interpretation -> information retrieval -> judgement formation -> response formatting -> response editing

Context effects

unintended influences on respondents’ answers because they are not related to the content of the item but to the context in which the item appears

ADD!!!

Item-order effect

when the order in which the items are presented affects people’s responses

Open-ended items

simply ask a question and allow participants to answer in whatever way they choose

Closed-ended items

questionnaire items that ask a question and provide a limited set of response options for participants to choose from

Rating scale

an ordered set of responses that participants must choose from

Likert scale

0-10 satisfaction

Created by Rensis Likert to measure people’s attitudes

refers to attitude measures only

BRUSO

used to create effective questionnaire items that are brief and to the point

Stands for brief, relevant, unambiguous, specific, and objective

Probability sampling

occurs when researcher can specify the probability that each member of the population will be selected for the sample

ADD!!!

Non-probability sampling

occurs when the researcher cannot specify the probability that each member of the population will be selected for the sample

ADD!!!

convenience sampling

common method of non-probability sampling in which the sample consists of individuals who happen to be easily available and willing to participate

Snowball sampling

form of non-probability sampling in which existing research participants help recruit additional participants for the study

Quota sampling

form of non-probability sampling in which subgroups in the sample are recruited to be proportional to those subgroups in the population

ADD!!!

Self-selection sampling

form of non-probability sampling in which individuals choose to take part in the research on their own accord, without being approached by the researcher directly

Sampling frame

list of all the members of the population from which to select the respondent

ADD!!!

Simple random sampling

probability sampling method in which each individual in the population has an equal probability of being selected for the sample

Stratified random sampling

a common alternative to simple random sampling in which the population is divided into different subgroups or strata (usually based on demographic characteristics) and then a random sample is taken from each stratum

ADD!!!

Proportionate stratified random sampling

is used to select a sample in which the proportion of respondents in each of various subgroups matches the proportion in the population

ADD!!!

Disproportionate stratified random sampling

is used to sample extra respondents from particularly small subgroups, allowing valid conclusions to be drawn about those subgroups

ADD!!!

Cluster sampling

type of probability sampling in which larger clusters of individuals are randomly sampled and then individuals within each cluster are randomly sampled

ADD!!!

Sampling bias

occurs when a sample is selected in such a way that it is not representative of the entire population and therefore produces inaccurate results

Non-response bias

occurs when there is a systemic difference between survey non-responders from survey responders

ADD!!!

Key takeaways from Ch. 7

• Most survey research is non-experimental in nature (it is used to describe variables or measure statistical relationships between variables) but surveys can also be used to measure dependent variables in true experiments

• Survey responses are subject to numerous context effects due to question wording, item order, response options, and other factors. Researchers should be sensitive to such effects when constructing surveys and interesting survey results

• Use verbal labels instead of numerical labels although responses can be converted to numerical data in the analyses

• Survey research usually involves probability sampling, in which each member of the population has a known probability of being selected for the sample. Types of probability sampling include simple random sampling, stratified random sampling, and cluster sampling

• Sampling bias occurs when a sample is selected in such a way that it is not representative of the population and therefore produces inaccurate results. The most pervasive form of sampling bias is non-response bias, which occurs when people who do not respond to the survey differ in important ways from people who do respond. The best way to minimize non-response bias is to maximize the response rate by prenotifying respondents, sending them reminders, constructing questionnaires that are short and easy to complete, and offering incentives

Nine sources of threat to internal validity

• Selection

• History

• Maturation

• Repeated testing

• Instrumentation

• Regression to the mean

• Experimental mortality

• Selection-maturation interaction

• Experimenter bias

Clever Hans effect

Animals respond to cues from humans

ADD!!!

Waitlist control groups

Compare treatment to people who are waiting to get treatment

Not neutral

Simplest Experimental Design

Pre-test vs post-test

Solomon Four-Group Design

ADD!!!

Ethics

Branch of philosophy that is concerned with morality- what it means to behave morally and how people can achieve that goal

4 general moral principles that apply to scientific research

weighing risks against benefits

acting responsibly and with integrity

seeking justice

respecting people’s rights and dignity

(adapted from APA ethics code)

Who is affected by scientific research?

research participants

scientific community

society

confederate

helper who pretends to be real participant in study

Tuskegee Syphilis Study

poor Black men from Alabama were observed to see how syphilis developed and were denied treatment

autonomy

persons right to make their own choices and take their own actions free from coercion

informed consent

researchers obtain and document people’s agreement to participate in a study after having informed them of everything that might reasonably be expected to affect their decision

privacy

a person’s right to decide what information about them is shared with others

confidentiality

an agreement not to disclose participants’ personal information without their consent or some appropriate legal authorization

anonymity

when a participants name and other personally identifiable information is not collected at all

Nuremberg Code

one of the earliest ethics codes

a set of 20 ethical principles for research written in 1947 in conjunction with the Nuremberg trials of Nazi physicians accused of war crimes against prisoners in concentration camps

Declaration of Helsinki

ethics code created by the World Medical Council in 1964

Similar to Nuremberg Code

research on humans should be based on protocols that is reviewed by independent committee

most recently revised in 2004

protocol

detailed description of research that is reviewed by independent committee

Belmont Report

set of federal guidelines written in 1978 as a response to the abuses of the Tuskegee study that recognize three important principles in research with humans: justice, respect for persons, and beneficence

formed basis for federal regulations applied to research

justice

importance of conducting research in a way that distributes risks and benefits fairly across different groups at the societal level