Hypothesis Formation

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Hypothesis Formation
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Hypothesis

• The main idea or thesis of an experiment
• But there may be several hypotheses
• Definition a statement about the predicted or
  expected relationship between at least two
  variables
• NOT simply a question, notion, or vague idea
• That is, a level of precision/specificity is
  required

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A good hypothesis directs what you do in a study.
Psy 301
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Hypotheses for different types of studies

• Experimental hypothesis for true experiments
  where variables are manipulated and outcomes
  measured, the hypothesis is a cause and effect
  statement
• Y will occur, if X is changed
• Example Students will remember more items from a
  word list if they learn the list in the quiet,
  rather than in the presence of intense (100 dB
  SPL) music (Rolling Stones, Satisfaction).
• Example Reading speed (words/minute) will change
  when font size is manipulated, such that reading
  speed will increase as font size is increased
  from 4 point to 20 point, but reading speed will
  decrease as font size is increased above 20 point

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Hypotheses for different types of studies

• Non-experimental hypothesis for studies
  examining the relationships between variables
  such as personality traits, work habits, gender,
  etcetera, the hypothesis is a specific statement
  about relationships
• If when we observe an increase in X then we will
  also observe and increase (or decrease) in Y
• example Gender will be related to the empathy
  subscore on the MMPI such that females will score
  higher (be more empathetic) than males

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Characteristics of a good hypothesis

• Testable
• The means for manipulating the variables and/or
  measuring the outcome variable must potentially
  exist
• Falsifiable
• must be able to reject the hypothesis with data
• Parsimonious
• should be stated in simplest adequate form
• Precise
• Should be specific (operationalized)
• Useful
• Relate to existing theories and/or point toward
  new theories
• it should lead to studies beyond the present one
  (often hard to determine in advance)

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Psy 301
Example hypothesis
Watching violent television programs makes
children more aggressive.
Is this a good hypothesis?
NO. The variables need to be operationally
defined to be unambiguous.
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Psy 301
Example hypothesis
Watching violent television programs makes
children more aggressive.
What is meant by watching?
What is meant by violent television programs?
What is meant by children?
What is meant by more aggressive?
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Psy 301
Other examples
The size of a meeting is related to the length of
the meeting.
Exercise is related to levels of stress.
Jury decisions are influenced by the
attractiveness of the defendant.
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Clear, Concise, Precise

• Vague words or indefinite words should be
  avoided.
• may - this may affect that
• somewhat - this will increase somewhat
• often - this often affects that
• likely - this will likely influence that
• enough - if there is enough of this, then
• sometimes - this will sometimes affect that
• Be specific when using these
• affect
• influence
• interact with
• related to

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Other considerations during hypothesis formation

• Independent variables
• how many?
• how many levels each?
• what range of IV (floor ceiling effects)
• Dependent variables (usually 1 but can be more)
• construct validity
• is measure obtrusive, will it induce reactivity?
• is measure sensitive enough?

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Statistical Hypotheses

• The Null Hypothesis (H0)
• What you are trying to falsify
• The Alternate Hypothesis (Ha)
• What you think is true
• Example (One-tailed) Students will remember more
  items from a word list if they learn the list in
  the quiet, rather than in the presence of intense
  (100 dB SPL) music (Rolling Stones,
  Satisfaction).
• H0 ?q?m
• Ha ?qgt?m
• Example (Two-tailed) Students will perform
  differently on word list recall if they learn
  the list in the quiet, rather than in the
  presence of intense (100 dB SPL) music (Rolling
  Stones, Satisfaction).
• H0 ?q?m
• Ha ?q? ?m
• Less Power