Statistics 101 (An Introduction)
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Transcript Statistics 101 (An Introduction)
Introduction to Statistical Methods
Session 3
Univariate Data
Daniel D Reidpath
28 June 2011
Kinds of statistics
Location
Spread
Mean, 25th percentile, Mode
Range, variance, standard deviation
Shape
Uniform, “Normal”
Interrelationship/Difference
Fit
Kinds of Data
Ratio data
Interval data
2Y is twice as big as Y
The difference between Y+2 and Y+5 is 3
Ordinal data
Sometimes treated as truly ordered data
Sometimes treated as a “Factor”
Sometimes treated as interval or
even ratio (*sigh*)
Kinds of Data...
Nominal
Factors
Groups
Binary/Dichtomous
Logical (True/False)
Nominal
Missing
Nominal Data
• In general the numerical descriptions for
nominal data are
• Frequencies – counts
• Percentages or Proportions
• The common visual plot for nominal data is
the barchart (or in R .. The barplot() )
• Load Session3.R and have a look at the
Titanic Data
Ordinal Data
• Numerical Descriptions for ordinal data
include medians, range and quartile range
• The typical plot is the boxplot.
• Using Session3.R, have a look at the
famous Iris data from RA Fisher.
Photograph by Eric Guinther
Continuous Data
• Common summary descriptions for data
involve some kind of central point measure,
and some measure of variation.
• What would be good for continuous data?