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Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Dec 21, 2015

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independent variable

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extraneous variation

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Page 1: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 2: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 3: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Criteria for Establishing Causal Relationships

• Concomitant variation

• Temporal ordering of variables

• Control over other possible causal factors

Page 4: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 5: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 6: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 7: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Threats to Internal Validity

Page 8: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 9: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 10: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
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Page 12: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 13: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 14: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 15: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
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Page 18: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 19: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 20: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 21: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 22: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 23: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 24: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 25: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Experiment

• A research investigation in which conditions are controlled

• One independent variable is manipulated (sometimes more than one)

• Its effect on a dependent variable is measured

• To test a hypothesis

Page 26: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Basic Issues of Experimental Design

• Manipulation of the Independent Variable

• Selection of Dependent Variable

• Assignment of Subjects (or other Test Units)

• Control Over Extraneous Variables

Page 27: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

The experimenter has some degree of control over the independent variable. The variable is independent because its value can be manipulated by the experimenter to whatever he or she wishes it to be.

Page 28: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Experiment Treatment

Alternative manipulations of the independent variable

being investigated

Page 29: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Independent Variable

• The experimenter controls independent variable.

• The variable’s value can be manipulated by the experimenters to whatever they wish it to be.

Page 30: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Manipulation of Independent Variable

• Classificatory vs. continuous variables

• Experimental and control groups

• Treatment levels

• More than one independent variable

Page 31: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Experimental Treatments

• The alternative manipulations of the independent variable being investigated

Page 32: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Dependent Variable

• Its value is expected to be dependent on the experimenter’s manipulation

• Criterion or standard by which the results are judged

Page 33: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Dependent Variable

• Selection–e.g... sales volume, awareness,

recall,

• Measurement

Page 34: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Test Units

• Subjects or entities whose response to the experimental treatment are measured or observed.

Page 35: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Two Types of Experimental Error

• Constant errors• Random errors

Page 36: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Field versus Laboratory Experiments

Page 37: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Controlling Extraneous Variables

• Elimination of extraneous variables

• Constancy of conditions

• Order of presentation

• Blinding

• Random assignment

Page 38: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

How May an Experimenter control forExtraneous Variation?

• Eliminate Extraneous Variables

• Hold Conditions Constant

• Randomization

• Matching Subjects

Page 39: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Demand Characteristics

• Experimental procedures that intentionally hint to subjects something about the experimenter’s hypothesis

Page 40: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Demand Characteristics

• Guinea pig effect

• Hawthorne effect

Page 41: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Field vs. Laboratory Experiment

Page 42: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Laboratory Experiment Field Experiment

Artificial-Low Realism

Few ExtraneousVariables

High control

Low Cost

Short Duration

Subjects Aware ofParticipation

Natural-High Realism

Many ExtraneousVariables

Low control

High Cost

Long Duration

Subjects Unaware ofParticipation

Page 43: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Control Groups

Isolate extraneous variation

Page 44: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

When does an Experiment have Internal Validity?

Internal Validity - The ability of an experiment to answer the question whether the experimental treatment was the sole cause of changes in a dependent variable

Did the manipulation do what it was supposed to do?

Page 45: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Factors Influencing Internal Validity

• History

• Maturation

• Testing

• Instrumentation

• Selection

• Mortality

Page 46: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Isolating Extraneous Variationwith a Control Group

• History Effects

• Maturation Effects

• Mortality Effects

Page 47: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Type of Extraneous Variable Example

History - Specific events in theenvironment between the Beforeand After measurement that are beyond the experimenter’s control

Maturation - Subjects changeduring the course of the experiment

Testing - The Before measure alertsor sensitizes subject to nature of experiment or second measure.

A major employercloses its plant intest market area

Subjects become tired

Questionnaireabout the traditionalrole of women triggers enhanced awareness of womenin an experiment.

Page 48: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Instrument - Changes ininstrument result in response bias

Selection - Sample selectionerror because of differentialselection comparison groups

Mortality - Sample attrition; some subjects withdraw from experiment

New questions aboutwomen are interpreteddifferently from earlierquestions.

Control group and experimental group isself-selected groupbased on preference forsoft drinks

Subjects in one groupof a hair dying study marry rich widows and move to Florida

Page 49: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

Increasing Internal Validity

• Control group

• Random assignment

• Pretesting and posttesting

• Posttest only

Page 50: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 51: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.
Page 52: Criteria for Establishing Causal Relationships Concomitant variation Temporal ordering of variables Control over other possible causal factors.

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