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Grouped vs. Ungrouped Data
Grouped Data –
Data
that has been organized
into groups (into a frequency distribution).
If you see a table similar to the one below, you will know that you are
dealing with grouped data:
Class
Frequency
0 – 5
4
6 – 10
5
The frequency of a class is
11 – 15
12
the number of numbers in
16 – 20
7
that class. For example, there
must have been four numbers
between 0 and 5.
Ungrouped Data –
Data
that has not
been organized
into groups.
Ungrouped data looks like a big ol’ list of numbers.
How to Group Data
On your exam, you may have to construct a frequency distribution.
Constructing a
frequency distribution is the same thing as grouping data.
The first step in grouping data is deciding how large of a class interval to use.
(Class interval = Class size)
There are 2 formulas for determining the appropriate class interval.
You must be able to
choose which one would be appropriate for any given problem.
1. Class interval
=
Use when the problem states
the
number of classes to be used.
2.
Class interval
=
Use when the problem does not
state
the number of classes to be
used.
**Don’t forget to always round up to the nearest whole number
when dealing with
class interval
.**
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View Full Document Populations vs. Samples
Population –
A collection of all possible
individuals, objects, or measurements (Mason
7).
Please note that a population does not have to be huge in size. It is all a matter of how
the objects in the group are defined.
For example, if we wanted to compute the average
GPA of the population of students taking BA254 at GRCC in the summer of 2002, our
population would only include approximately 75 people.
On the other hand, if we
wanted to find the average GPA of all students who have ever taken BA254 at GRCC, we
would be dealing with a much larger number of students.
This is because of how each population was defined. In the first example, we gave our
population a definition that severely limited the number of GPA’s that would be included.
The second population was defined a little more broadly, and, therefore, more students
would fall under this definition.
Sample –
A portion or part
of
the population.
(Mason 7)
Measures of Central Tendency
Central Tendency
– Where the numbers tend to cluster.
Where most of the numbers are at.
A single value that summarizes a set of data by locating the center
of the data (Mason 65).
4 Basic Measures of Central Tendency:
1. The Mean = The Average = The Arithmetic Mean
2. The Median = The Middle (of the road)
50% of the data fall above the median, and 50% fall below the median.
3. The Mode = The Most
The mode is the number(s) that appear(s) the most out of a given set of data.
A
data set can have more than one mode value.
4. Geometric Mean = G.M.
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This note was uploaded on 12/07/2011 for the course MBA 0001 taught by Professor Akshat during the Spring '09 term at Institute of Management Technology.
 Spring '09
 Akshat

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