By Attaullah Khan
Refers to methods and
techniques used for describing,
organizing, analyzing, and
interpreting numerical data.
Statistics is often categorized
into descriptive and
Types of statistics:
• Descriptive (which summarize some characteristic of a sample)
• Measures of central tendency
• Measures of distribution
• Measures of skewness
• Inferential (which test for significant differences between groups
and/or significant relationships among variables within the sample
• t-ratio, chi-square, beta-value
• Univariate analysis involves the
examination across cases of one
variable at a time. There are three
major characteristics of a single
variable that we tend to look at:
• the distribution
• the central tendency
• the dispersion
In most situations, we would describe
all three of these characteristics for
each of the variables in our study.
students take an
samples 1,000 students
Used to describe
Based on descriptive
statistics to estimate
scores of the entire
population o 100,000
Thus, descriptive statistics are
used to classify, organize, and
summarize numerical data about a
particular group of observations.
There is no attempt to generalize
these statistics, which describe
only one group, to other samples
Methods of describing the
characteristics of a data set.
Useful because they allow you
to make sense of the data.
Helps exploring and making
conclusions about the data in
order to make rational decisions.
Includes calculating things such
as the average of the data, its
spread and the shape it
In other words, descriptive statistics are used to
summarize, organize, and reduce large
numbers of observations.
Descriptive statistics portray and focus on what
is with respect to the sample data, for example:
What percentage of students want to go to
Percentage and Graphs
Central Tendency and Variation
• A frequency distribution is a table that shows classes or intervals of
data with a count of the number in each class. The frequency f of a
class is the number of data points in the class.
• Pie or Bar Chart or Histogram
• Stem and Leaf Plot
• Frequency Polygon
A pie chart is a circle that is divided
into sectors that represent categories.
The area of each sector is
proportional to the frequency of each
Central Tendency (or Groups’ “Middle Values”)
Mean, Median, Mode
Variation (or Summary of Differences Within