UNIVARIATE ANALYSIS

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UNIVARIATE ANALYSIS

• CHAPTER 13
• SURVEYS IN SOCIAL RESEARCH
• DE VAUS

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FREQUENCY DISTRIBUTION, STEM AND LEAF DISPLAY,
HISTOGRAMS

• What is a frequency distribution? How do we set
  up a frequency distribution from data?
• What is a stem-and-leaf display?
• What is a histogram?

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DATA COLLECTED BY NURSES IN AN OPERATING THEATRE
THESE ARE THE TIMES REQUIRED TO PERFORM THE SAME
NEUROSURGICAL PROCEDURE ON 60 PATIENTS
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Neurosurgical procedure times

• Besides operating times, other details recorded
  about the patients
• such as age, length and type of illness,
  gender, complications during procedure, years of
  experience of surgeon.

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Some possible questions nurses would want to
answer with data like these!!

• How can such data help with rostering?
• What should I say if a patients relative asked
  about the expected length of the operations?
• Do some operations take longer than others? Why
• Does speed of operation relate to a successful
  outcome?

• Do we have adequate nursing support staff?
• Do some surgeons take longer time with the
  operation than others? Why?
• What are the implications of the data for use of
  the operating theatre for other operations?
• Can we use data like these to make a case for
  more funding to cope with the increasing demand
  for an operation like this?

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ANALYSIS TIME!
Raw Data
Information
New Knowledge
Data Analysis
Informed decision-making
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Frequency Distribution
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Answering those questions!

• 15 out of 60(25) operations take less than 9
  hours
• A little over half (33/60) last less than 10
  hours
• 95 of the operations are completed within 13
  hours
• Most of the operations(70) take between 8 and 11
  hours
• Some operations took longer than others Could
  it be that the patients were more seriously ill?,
  were they older?, were surgeons less
  experienced?. Could the purchase of more
  sophisticated equipment shorten the operating
  time?
• No operating time took last than 7 hours!!!

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STEM-AND-LEAF PLOT FOR OPERATING TIMES DATA
(UNORDERED)

• 7 982
• 8 656127306976
• 9 034178892346715665
• 10 782129318963
• 11 5012841
• 12 34945
• 13 37
• 14
• 15 6

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STEM-AND-LEAF PLOT FOR OPERATING TIMES DATA
(ORDERED)

• 7 289
• 8 012356666779
• 9 011233445566677889
• 10 1122334455666777889
• 11 0112458
• 12 34459
• 13 37
• 14
• 15 6

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HISTOGRAM FOR THE OPERATING TIMES

• DETERMINE THE RANGE, WHICH IS 15.7 7.3 8.4
  HOURS
• IF WE DECIDE TO HAVE 9 INTERVALS, THEN THE
  INTERVAL WITH IS APPROX 8.4/9 0.9
• THE INTERVALS WILL BE 7.0-7.9, 8.0-8.9, 9.0-9.9
  AND SO ON UNTIL THE FINAL INTERVAL, 15.0-15.9

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