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Chapter 4 Gathering Useful Data for Examining Relationships by Mind Map: Chapter 4 Gathering Useful Data
for Examining Relationships
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Chapter 4 Gathering Useful Data for Examining Relationships

4.1 Speaking the Language of Research Studies

Types of Research Studies

Observational Studies, Researchers simply observe or question the participants about opinons, behaviors, or outcomes

Experiments, Experiment, Researchers manipulate something and measure the effect of the manipulation on some outcome of interest, Randomized Experiment, Participants are randomly assigned to participate in one condition or another, Treatments are the different "conditions"

Who is measured : Units,Subjects, Participants

Researchers use a variety of terms to describe who is measured such as unit,experimental unit,subjects, and participants

Explanatory and Response Variables

An explanatory, somtimes called an independent variable, is one that may explain or may cause differences in a response variable

A response variable, sometimes called an outcome or dependent variable

Confounding Variables -Measured or Not

A confounding variable affects the response variable and is related to the explanatory variable

Lurking variable: a possible confounding variable not measured or considered in the interpretation of the study

4.2 Designing a Good Experiment

Who Participates in Randomized Experiments?


Randomization: The Crucial Element

In experimentation we want to make sure that the experimenters do not have the flexibility to choose which of the units receive each of the potential treatments

Control Groups, Placebos, and Blinding

Control Groups: treated identical except do not receive treatment

Placebos: looks like the real treatment but has not active ingredients

Blinding, Double Blind experiment is one in which neither the participant nor the researcher taking the measurements knows who had the treatment, Single Blind experiment is one in which the participants do not know which treatmentthey have been assigned, Double Dummy is used in an experiemnt to compare two treatments, so each group receives on treatment and one placebo

Design Terminology and Examples

Completely Randomized


Randomized Block, Repeated-Measure

4.3 Designing a Good Observational Study

Types of Observational Studies

Retrospective and Prospective Studies, A retrospective study uses data from the past, A prospective case study follows particiapnts into the future and uses data from the future time

Case-Control Studies, Compares individuals with a condition and individuals without the condition to determine whether cases and controls differ with respect to explanatory variables of interest

Advantages of Case-Control Studies


Reduces Potential Confounding Variables

4.4 Difficulties and Disasters in Experiments and Observational Studies

Confounding Variables and The Implication of Causation in Observational Studies

Hawthorne and Experimenter Effects

The Hawthorne effect is when participants respond differently than normal, simple because they are in an exaperiment

Experimenter effects include recording data to match desired outcome, treating units differently depending on the treatment being given, and making participants aware of the desired outcome

Ecological Validity and Generalizability

RULE for Concluding Cause and Effect: cause-and-effect relationships can be inferred from randomized experiments but not observational studies

Extending results inappropriatley

Interacting variables

Using the past as a source for data