These slides contains some basic descriptive statistics.

1. Basic Statistics : Descriptive Statistics

2. What is Descriptive
Statistics ? “ This is the statistics which deals with
descriptive section of the data set as well
as have tendency to describe the data set
initially ”

3. Commonly used measures to describe a data set :
 Measures of Central Tendency
 Measures of dispersion

4. Measures of Central Tendency:
A measure of central tendency is a single value
that attempts to describe a set of data by
identifying the central position within that set of
data. The mean, median and mode are most
likely the measures of central tendency that we
are most familiar with.
Mean (Arithmetic) :
The mean (or average ) is equal to the sum of all
the values in the data set divided by the number
of values in the data set. So, if we have n values in
a data set and they have values x1, x2, ..., xn, the
sample mean, usually denoted by (pronounced x
bar), is:

5. Median
The median is the middle score for a set of data that has been arranged in order
of magnitude.
Mode :
The mode is the value that appears most often in a set of data.

6. Measures of dispersion
Range:
The spread, or the distance, between the
lowest and highest values of a variable.
Interquartile Range:
A quartile is the value that marks one of the
divisions that breaks a series of values into
four equal parts. The Interquartile range is
the distance or range between the 25th
percentile and the 75th percentile.

7. Standard Deviation:
The standard deviation gives an idea of how close the entire set of data is to the average value.
Variance:
Measures how far a set of numbers is spread out. A variance of zero indicates that all the values
are identical. Variance is always non-negative, a small variance indicates that the data points
tend to be very close to the mean (Average value), while a high variance indicates that the data
points are very spread out around the mean.

8. Thank You