Experiment Basics: Variables

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Experiment Basics Variables

• Psych 231 Research Methods in Psychology

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Body

• Introduction

• Background
• Literature Review
• Statement of purpose
• Specific hypotheses (at least at conceptual
  level)

3
Body

• Methods (in enough detail that the reader can
  replicate the study)

• Participants
• How many
• Where they were selected from
• Any special selection requirements
• Details about those who didnt complete the
  experiment

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Body

• Methods (in enough detail that the reader can
  replicate the study)

• Participants

• Design (optional)
• Suggested if you have a complex experimental
  design, often combined with Materials or
  Procedure sections

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Body

• Methods (in enough detail that the reader can
  replicate the study)

• Participants
• Design

• Apparatus/Materials
• Procedure
• What did each participant do?
• Other details, including the operational levels
  of your IV(s) and DV(s), counterbalancing, etc.

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Body

• Results
• Verbal statement of results
• Tables and figures
• These get referred to in the text, but get put at
  the end of the manuscript
• Statistical Outcomes
• Means, standard deviations, t-tests, ANOVAs,
  correlations, etc.
• state the results but dont interpret them here

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Body

• Discussion - interpret the results
• Relationship between purpose and results
• Theoretical (or methodological) contribution
• Implications
• Future directions (optional)

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The rest

• References
• Authors name
• Year
• Title of work
• Publication information
• Journal
• Issue
• Pages

Adolescent Depression 29
References Barnett, P. A.,
Gotlib, I. H. (1988). Psychosocial
functioning and depression Distinguishing among
antecedents, concomitants, and
consequences. Psychological Bulletin,
104. Beck, A. T. (1978). Beck Depression
Inventory. San Antonio, TX
Psychological Corporation. Benoit, D.,
Vidovic, D., Roman, J. (1991, April).
Transmission of attachment across three
generations. Paper presented at the
Biennial Meeting of the Society for
Research in Child Development. Benoit, D.,
Zeanah, C. H., Barton, M. L. (1989).
Maternal attachment disturbances in failure to
thrive. Infant Mental Health Journal,
3, 185-202. Benoit, D., Zeanah, C. H.,
Boucher, C., Minde, K. (1989). Sleep
disorders in early childhood Association
with insecure maternal attachment. Journal of
the American Academy of Child and
Adolescent Psychiatry, 31, 86-93.
When something odd comes up, dont guess. Look
it up!
9
The rest

• References

Adolescent Depression 29
References Barnett, P. A.,
Gotlib, I. H. (1988). Psychosocial
functioning and depression Distinguishing among
antecedents, concomitants, and
consequences. Psychological Bulletin,
104. Beck, A. T. (1978). Beck Depression
Inventory. San Antonio, TX
Psychological Corporation. Benoit, D.,
Vidovic, D., Roman, J. (1991, April).
Transmission of attachment across three
generations. Paper presented at the
Biennial Meeting of the Society for
Research in Child Development. Benoit, D.,
Zeanah, C. H., Barton, M. L. (1989).
Maternal attachment disturbances in failure to
thrive. Infant Mental Health Journal,
3, 185-202. Benoit, D., Zeanah, C. H.,
Boucher, C., Minde, K. (1989). Sleep
disorders in early childhood Association
with insecure maternal attachment. Journal of
the American Academy of Child and
Adolescent Psychiatry, 31, 86-93.


Adolescent Depression 29
Authors Notes This work
was funded in part through a grant from the
Center For Teaching and Illinois State
University. The authors would Like to thank
Jack Smith and Jill Doe and two reviewers for
Their useful feedback.


Adolescent Depression 29
Footnotes 1 It has been
pointed out that the way in which we use the Term
attention is different from how it has commonly
been Used in earlier work on perceptual
integration. 2 An alternative approach
to this issue would be to use a Masked priming
paradigm. We are currently investigating This
potential in our laboratory.

• Authors Notes
• Footnotes
• Tables
• Figure Captions
• Figures

Adolescent Depression 29
Figure Captions Figure 1.
Presents the condition means from Experiment 1
Figure 2. Presents the conditino means from
Experiment 2
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Figures and tables

• These are used to supplement the text.
• To make a point clearer for the reader.
• Typically used for
• Patterns of results
• The design
• Examples of stimuli

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Checklist - things to watch for

• 1 Clarity - say what you want to say
• Acknowledge the work of others (avoid plagiarism)
• Active vs. passive voice (avoid passive)
• Active Monroe and Coey (2003) hypothesized that
  speakers use to much passive voice
• Passive It was hypothesized by Monroe and Coey
  (2003) that speakers use to much passive voice

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Checklist - things to watch for

• Avoid biased language
• APA guidelines
• Accurate descriptions of individuals (e.g., Asian
  vs. Korean)
• Be sensitive to labels (e.g., Oriental)
• Appropriate use of headings
• Correct citing and references
• Good grammar

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So you want to do an experiment?

• Youve got your theory.

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So you want to do an experiment?

• Youve got your theory.

• What behavior you want to examine
• Identified what things (variables) you think
  affects that behavior

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So you want to do an experiment?

• Youve got your theory.
• Next you need to derive predictions from the
  theory.
• These should be stated as hypotheses.
• In terms of conceptual variables or constructs

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So you want to do an experiment?

• Youve got your theory.
• Next you need to derive predictions from the
  theory.
• Now you need to design the experiment.
• You need to operationalize your variables in
  terms of how they will be
• Controlled
• Manipulated
• Measured
• Be aware of the underlying assumptions connecting
  your constructs to your operational variables

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An example

• Hypothesis Eating candy with peanuts improve
  memory performance
• How might we test this with an experiment?

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Constants vs. Variables

• Characteristics of the psychological situations
• Constants have the same value for all
  individuals in the situation
• Variables have potentially different values for
  each individual in the situation

• Constants
• MMs are eaten
• Variables
• Type of MM peanut vs plain
• Memory performance

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Variables

• Conceptual vs. Operational
• Conceptual variables (constructs) are abstract
  theoretical entities
• Operational variables are defined in terms within
  the experiment. They are concrete so that they
  can be measured or manipulated

Conceptual Peanut candies Memory
Operational Peanut MMs Memory test
Underlying assumptions
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Variables

• Independent variables (explanatory)
• Dependent variables (response)
• Extraneous variables
• Control variables
• Random variables
• Confound variables

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Independent Variables

• The variables that are manipulated by the
  experimenter (sometimes called factors)
• Each IV must have at least two levels
• Remember the point of an experiment is comparison
• Combination of all the levels of all of the IVs
  results in the different conditions in an
  experiment

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Independent Variables

• 1 factor, 2 levels

1 factor, 3 levels
2 factors, 2 x 3 levels
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Choosing your independent variable

• Methods of manipulation
• Straightforward manipulations
• Stimulus manipulation - different conditions use
  different stimuli
• Instructional manipulation different groups are
  given different instructions
• Staged manipulations
• Event manipulation manipulate characteristics
  of the context, setting, etc.
• Subject manipulations there are (pre-existing
  mostly) differences between the subjects in the
  different conditions (leads to a quasi-experiment)

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Choosing your independent variable

• What about our candy experiment?

1 IV Candy type (3 levels)
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Dependent Variables

• The variables that are measured by the
  experimenter
• They are dependent on the independent variables
  (if there is a relationship between the IV and DV
  as the hypothesis predicts).

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Choosing your dependent variable

• How to measure your your construct
• Can the participant provide self-report?
• Introspection specially trained observers of
  their own thought processes, method fell out of
  favor in early 1900s
• Rating scales strongly agree-agree-undecided-di
  sagree-strongly disagree
• Is the dependent variable directly observable?
• Choice/decision (sometimes timed)
• Is the dependent variable indirectly observable?
• Physiological measures (e.g. GSR, heart rate)
• Behavioral measures (e.g. speed, accuracy)

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Choosing your dependent variable

• Conceptual level Memory

• What about our candy experiment?

• Operational level Some kind of memory test
• Memorize a list of words while eating the candy
  
• Then 1 hour after study time, recall the list of
  words
• Measure the accuracy of recall

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Extraneous Variables

• Control variables
• Holding things constant - Controls for excessive
  random variability

• Number of MMs consumed
• Time of day test taken

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Extraneous Variables

• Random variables may freely vary, to spread
  variability equally across all experimental
  conditions
• Randomization
• A procedures that assure that each level of an
  extraneous variable has an equal chance of
  occurring in all conditions of observation.
• On average, the extraneous variable is not
  confounded with our manipulated variable.

• What your participants ate before the
• experiment

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Control your extraneous variable(s)

• Can you keep them constant?
• Should you make them random variables?
• Two things to watch out for
• Experimenter bias (expectancy effects)
• the experimenter may influence the results
  (intentionally and unintentionally)
• E.g., Clever Hans
• One solution is to keep the experimenter blind
  as to what conditions are being tested
• Demand characteristics cues that allow the
  participants to figure out what the experiment is
  about, influencing how they behave

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Confound Variables

• Confound variables
• Other variables, that havent been accounted for
  (manipulated, measured, randomized, controlled)
  that can impact changes in the dependent
  variable(s)

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Next time

• Read chapters 3 5.
• Bring your textbook and/or APA Publication Manual
  to lab (if youve got one)
• Dont forget your first journal summary is due
  this week in lab