chapter_7_examples rm angel (1)
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Research Methods chp 7TRANSCRIPT
Variables, Measurement
Issues, & Psychometrics
Chapters 5 & 7
Experimentation Experimental Hypothesis
Experiment
Experimental Procedure
Experimental Variables Variable
An event or characteristic that can take on at least two values
Independent Variable The variable in a study that is being
manipulatied
Subject Variable A characteristic. Attribute of a participatnt
Dependent VariableThe variable in a study that is observed or
measured
Extraneous Variables Variables out of control
Experimental Conditions Treatment Conditions
Levels of the independent variable (number of groups)
Common Treatment Conditions Experimental Condition: exposed to the IV Control Condition: Not exposed to the IV Placebo Control Condition
The group that is exposed to an inert substance or object that is similar to the independent variable but has no effect
Experimental Design In a well designed experiment, the only
difference between the experimental and control conditions is the independent variable
Levels of the Independent Variable Basic Experiment
Two groups: experimental and Control Condition Two levels of the independent variable
Multiple Levels of the Independent Variable Most research manipulates the IV at more than
two levels Allows us to better understand the influence of
the IV
ExamplesCaffeine on Alertness
Group 1: 8 oz coffeeGroup 2 : 24 oz coffeeGroup 3 : no coffee
Screen size on Reaction Time
Group 1: 17 inchesGroup 2: 19 inchesGroup 3 : 21 inches
Selecting Dependent Variables Behavioral Measures
Measures that investigate behavior Attitudinal Measures
Measures that assess one’s attitudes about a topic
Cognitive Measures Measures of one’s mental ability or knowledge
of a topic
Physiological Measures Measures that are biological in nature (ie, pulse
rate)
Multiple Dependent Measures Most studies assess more than one dependent
variable to increase the amount of information collected
Measuring Dependent Variables Measurement
The assignment of numerical values to a variable of interest
Levels of Measurement
Measuring Dependent Variables Restriction of Range
Scores cluster at the top or bottom of the scale Floor Effects: scores cluster at the bottom of the
scale Ceiling Effects: scores cluster at the top of the
scale
Operational Definitions Operational Definition
Procedure by which a variable is defined solely in terms of the observable procedures used to manipulate and measure it
Variables can be very broad; definition makes it more specific
Hypothetical Constructions Many variables of interest in psychology are
hypothetical constructs that cannot be directly observed
Operationalizing variables is critical for: Careful measurement Replication
Psychometrics Reliability
The consistency of a measure
Validity The accuracy of a measure
Measure assesses intended construct Measure assesses all aspcts of the intended construct Measure does not assess unintended constructs
Reliability is a necessary, yet insufficient condition for validity An unreliable measure is likely invalid A reliable measure is not a guarantee of validity
Measurement Error Observed Score
Actual score obtained from measurement observed score= true score + measurement
True Score Actual Degree of the trait of a person possesses
Measurement Error Random Error
Fluctuates with ach measurement May result in unreliable, invalid measurements
Systematic Error Present every time a measurement is made May result in reliable, yet invalid measurements
Assessing Reliability Consistency Across Time
Test-Retest Reliability
Consistency Across Forms Alternate/Parallel Forms Reliability
Inter-Rater (Inter-Observer) Reliability
Consistency Among Items Split-Half Reliability
Inter-Item Reliability (Internal Consistency)
Example: Inter-Rater Reliability Two managers rate an employee on
three skills needed for the job. Are the ratings reliable: consistent
between raters?
Example: Test-Retest Reliability A researcher develops a new
intelligence measure and wants to test its reliability. Are the scores reliable: consistent over
time?
Example: Inter-Item Reliability A researcher develops a 4-item survey
to measure brand loyalty and wants to test its reliability. Are the scores reliable: consistent among
items?
Validity of the IV Manipulation Check
An experiment is designed to test the effects of social status on assertiveness.
Types of Validity Statistical Conclusion Validity
Internal Validity
Construct Validity
External Validity
Measurement of Test Validity Content Validity
A researcher gives a test to measure personality. A group of SMEs judge it’s
content validity. Does the test content seem to be measuring personality?
Low Content Validity High Content Validity
Measurement of Test Validity Criterion-Related Validity
Construct Validity
Example: Criterion Validity ETS uses the GRE to predict students’
readiness in college. To test the validity of the GRE, scores may be compared to students’ GPAs. Is the GRE a good predictor of readiness?
Do scores on the GRE predict GPA?
Example: Criterion Validity A researcher develops a new measure
of sales aptitude and wants to test whether it is a good measure of sales performance. Can scores on the sales aptitude test predict
dollar sales?
Example: Construct Validity A researcher develops a new self-report
measure of anxiety and wants to test its construct validity. Does the test measure anxiety?