2. INTRODUCTION TO MEASURE OF
CENTRAL TENDENCY:
• In Statistics measure of central tendency is a central
value for a probability distribution of the
given data:
• There are two type of Data:
> Ungroup
> Group
4. Mean:
• In statistics Mean refers to the “Average” that is used to
derive the central tendency of the given data. We use
Mean where the data is less scattered.
• Formula: (For Ungroup Data)
X=Sx
n
• Formula: (For Group Data)
X=Zfx
X = observation N=number
of observations F= frequecy
n
5. Median:
• Median is the “middle” value in the list of numbers. To
find the Median, we arrange the observations in
ascending order. If there is odd number of observations,
the Median is the middle value. If the observations are
in even numbers, the Median is the average of two
middle values.
> Median is used when the data is more scattered.
6. Median Ungrouped Data(ODD number
of observations):
• Formula:
Median = n+i e.g. 5,10,15,20,25
2
Median Ungrouped Data(Even number of observation)
• Formula:
Median= n/2 + (n/2+1) e.g. 5,10,15,20,25,30
2
7. Median (Group Data):
• Formula:
l + h Zf - c.f
f 2
Where;
l= lower class boundary
h= size of class boundary
f= median frequency
c.f= cumulative frequency of preceding value
Class Interval Frequency
10 14 6
15 19 8
20 24 10
25 29 12
30 34 18
8. MODE:
• Most repeated value in a set of data is said as Mode.
There may two or more than two modes in a data.
> Example:
7,8,6,7,84,7,3,2,7,8
9. MODE: (Group Data)
• Formula:
l + h (fm-fi)
• Example:
Class Interval Frequency
11 20 2
2i 3° 4
31 40 6
41 5° 8
51 60 10
Where;
l= lower class boundary of
modal group.
h=size of class boundary.
fm=frequency of modal
group.
f1= proceeding value of
modal
group.
