PSYC 275 Introduction to Research Methods

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PSYC 275Introduction to Research Methods

• SC C Chapter 8
• Measurement

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Measurement

• One of the areas of special interest to social
  and behavioral scientists
• Because the things that we measure (depression,
  personality, mental activity, attitudes) have no
  natural units.
• Proxy measures

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Got some spare time?

• Do we have more or less leisure time than we used
  to have?
• Two books, two opposing findings

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Got some spare time?

• The underlying problem is defining and measuring
  leisure time
• Time not on the job/in the office
• Time spent playing
• Get very different answers.

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Choosing Measures for your research

• One of the problems with measurement is choosing
  between measuring the right thing(s) versus
  measuring the easy things.
• Will the act of taking your measure interfere
  with the behavior you are attempting to measure?

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Measurement Basics

• We measure a property of a person or thing when
  we assign a number to represent the property.
• Instrument - We often use an instrument to make a
  measurement. We may have a choice of the units
  we use to record the measurements.

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Measurement basics

• The result of measurement is a numerical variable
  that takes different values for people or things
  that differ in whatever we are measuring.

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Know your variables

• How is the variable defined
• Is the definition reasonable?
• Some researchers will take data on more than one
  DV as a check for internal validity in their
  study.

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Measurements valid and invalid

• We need to decide between valid and invalid
  measures
• We wouldnt use big toe length to measure
  intelligence.

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Measurements valid and invalid

• A variable is a valid measure of a property if it
  is relevant or appropriate as a representation of
  that property.
• A measure is valid if it measures what it is
  supposed to measure

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Measurements valid and invalid

• Often a rate at which something occurs is a more
  valid measure than a simple count of occurrences.
• Who is a good driver?
• Number of accidents
• Number of accidents/miles of travel

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Measurements valid and invalid

• Predictive validity
• A measurement of a property has predictive
  validity if it can be used to predict success on
  tasks that are related to the property measured.
• How well or accurately does the measure predict
  things that it should predict?
• Beck Depression Inventory (BDI) predicts
  extensive clinical interview assessment of
  depression

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End Chapter 8