# Organizing Data

Shared by:
Categories
Tags
-
Stats
views:
4
posted:
5/16/2012
language:
English
pages:
35
Document Sample

```							Organizing Data
Suppose a researcher
wished to do a study on the
number of miles that the
employees of a large
department store traveled
to work each day.
The researcher first would
have to collect the data.
When data are collected in
original form, they are
called raw data.
The raw data for this example.
1    2    6    7    12   13   2    6    9    5

18   7    3    15   15   4    17   1    14   5

4    16   4    5    8    6    5    18   5    2

9    11   12   1    9    2    10   11   4    10

9    18   8    8    4    14   7    3    2    6
Frequency Distribution
Class Limits
(in miles)                   Tally              Frequency

1-3              ///// /////                  10
4-6              ///// ///// ////             14
7-9              ///// /////                  10
10-12             ///// /                      6
13-15             /////                        5
16-18             /////                        5
Total    50
A frequency distribution is
the organization of raw
data in table form, using
classes and frequencies.
Twenty-five army inductees were
given a blood test to determine
their blood type. The data set is:
A       B      B      AB      O

O      O       B      AB      B

B       B      O      A       O

A      O       O      O      AB

AB      A      O      B       A
Since the data is categorical,
discrete classes can be used.

Class       Tally        Frequency   Percentage

A           /////          5           20

B           ///// //       7           28

O           ///// ////     9           36

AB          ////           4           16
25          100
When the range of data is
large, the data must be
grouped into classes that
are more than one unit in
width.
Number of hours that boat
batteries lasted:
The lower class limit is 24
The upper class limit is 30
The class boundaries separate the
classes so there are no gaps.
Basic rule of class boundaries:
   The class limits should have the same
decimal place as the data, but the class
place value and end in a 5.
Class width is found by subtracting the lower class
limit of one class from the lower class limit of the
next class
The researcher must decide
how many classes to use
and the width of each class.
To construct a frequency
rules:
1. There should be between 5 and
20 classes.
   Although there is no hard and fast rule for
the number of classes contained in a
frequency distribution, it is of the utmost
importance to have enough classes to
present a clear description of the collected
data.
2. The class width should be an
odd number.
   This ensures that the midpoint of each
class has the same place value as the
data. The class midpoint (Xm) is obtained
by adding the lower and upper boundaries
and dividing by 2, or adding the lower an
upper limits and dividing by 2.

   Computer programs don’t follow this rule.
3. The classes must be mutually
exclusive.
   No overlapping class limits.

Age                      Age
10 – 20                   10 – 20
20 – 30                   21 – 30
30 – 40                   31 – 40
4. The classes must be continuous.
   Even if no values occur in a given class,
that class must be included in the
distribution.

   A class with zero frequency on either end
can be omitted.
5. The classes must be exhaustive.
   There should be enough classes to
accommodate all the data.
6. The classes must be equal in
width.
   This avoids a distorted view of the data.

   One exception occurs when there is an
open-ended distribution – i.e., it has no
specific beginning value or no specific
ending value.
Data set 3 represents the
record high temperatures
for each of the 50 states.
Construct a frequency
distribution using 7 classes.
Step 1
Determine the width of the classes.

   Find the range (highest minus the
lowest). [34]
   Divide by the number of classes you
want. [34/7]
   Round up to the nearest whole number.
[4.9 → 5.0]
Step 2

   The smallest datum is 100. Let’s start
there.

   Keep adding the class width to the lower
class limits until you have 7 classes
Step 3
   Determine class boundaries.
Step 4
   Tally the data
Step 5
   Find the frequencies.
Step 6
   Find the cumulative frequencies.
Assignment
Data set 1, construct a frequency
distribution for the 4 sets of data

```
Related docs
Other docs by yurtgc548
Real Options and VOIP
Raina EMF Trace IFA 1-2006