QUANTIFICATION

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QUANTIFICATION

• Brian C. King
• February 13, 2003
• MIS 515

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QUALITATIVE vs. QUANTITATIVE

• Qualitative methods are helpful for analyzing and
  understanding interface design
• Quantitative methods are helpful in understanding
  human interactions with machines
• Numerical and empirically testable methods

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GOMS

• Goals, Objects, methods, selection rules
• Keystroke-level model is the simplest
• Rarely used in formal analysis because the
  concepts have been integrated into interface
  design intuitively

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INTERFACE TIMING

• People perform tasks at different speeds
• Tasks are composed of elementary gestures
• Typical times, rather than individual times, work
  well for comparative analysis

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CONVENTIONS
K 0.2 sec Keying The time it takes to tap a
key on the keyboard P 1.1 sec Pointing The
time it takes a user to point to a position on
a display H 0.4 sec Homing The time it takes
a users hand to move from the keyboard to the
GID or from the GID to the keyboard M 1.35
sec Mentally preparing The time it takes a user
to prepare mentally for the next
step R Responding The time a user must wait
for a computer to respond to input
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CALCULATIONS

• Break down a task into simple gestures using GOMS
  components
• Harder to identify an M than an H, P, or K
• Additional terms
• String A sequence of characters
• Delimiter A marks the beginning or end of a
  string
• Argument Information supplied to a command

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PLACING MENTAL OPERATORS

• Rule 0 Initial insertion of candidate Ms
• Insert Ms in front of all Ks
• Rule 1 Deletion of anticipated Ms
• Assumes some M actions are included in other
  actions
• Rule 2 Deletion of Ms within cognitive units
• Use only one M for a contiguous sequence of
  characters

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PLACING MENTAL OPERATORS

• Rule 3 Deletion of Ms before consecutive
  terminators
• Use only one M as a terminator of related actions
• Rule 4 Deletion of Ms that are terminators of
  commands
• Eliminate Ms that are part of a constant string
• Rule 5 Deletion of overlapped Ms
• Eliminate Ms while waiting for a response

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MEASUREMENT

• Information theoretic efficiency
• What comes out divided by what goes in
• Represented by Information Efficiency E
• Defined as the minimum amount of information
  necessary to complete a task divided by the
  amount of information that has to be supplied by
  the user

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MEASUREMENT

• E1 no work is required and no work is done
• E0 user is required to provide unnecessary
  information
• Information is measured in bits way too much
  math that makes my head hurt
• If you understood the examples, please explain
  them to me
• Character efficiency is much nicer (like E)

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MEASUREMENT

• Fitts Law the smaller and further away an
  object is, the longer it takes to get to it
• Hicks Law the more choices you have, the longer
  it takes you to make a decision
• DUH!!!!!!!!!!

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EXAMPLES

• Temperature Converter has three versions
• Radio buttons
• Sliders
• Bifurcated
• Macintosh menu versus Windows menu

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DISCUSSION

• Interesting in theory but are they used in
  practice?
• If you design intuitively and with the general
  concepts in mind do you really need to measure
  down to milliseconds etc?
• What common software does not follow these
  concepts?