data presentation....................ppt

By
Sana Majeed
Post RN BScN, MA English, MPH

Data presentation
Data presentation is the method by which
people summarize, organize and
communicate information using a variety of
tools, such as diagrams, distribution charts,
histograms and graphs.
2

3
1. Frequency Table (frequency
distriution)
2. Graphs and charts
1. Histogram
2. Frequency polygon
3. Bar chart
4. Pie chart
5. stem-and-leaf display
6. Box Plot

Frequency Distributions Tables
Frequency Distributions Tables
 A frequency distribution
frequency distribution is the organizing of raw data
in table form, using classes and frequencies.
 When data are collected in original form, they are
called raw data.
 the raw data is organized into a frequency
distribution,
 frequency is the number of values in a specific
class of the distribution.

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Frequency Distribution
 A Tabular summary of a set of data showing the
frequency (or number) of items in each of
several non overlapping (with each data value
belonging to one and only one group) groups.
Tally Marks
 Used to count the number of data items
associated with each group.

9
Definitions
Class
 One of the categories in which qualitative data can
be classified.
 A range of value established to divide quantitative
data in to classes.
Class Frequency
 Number of observations in a data set falling into a
particular class.
Cumulative Frequency
 Number of observation in a data set falling below
or above particular class inclusive of that
particular class.

Three Types of Frequency
Three Types of Frequency
Distributions
Distributions
1.
1. Categorical frequency distributions
Categorical frequency distributions -
- can be used for
data that can be placed in specific categories, such
as nominal- or ordinal-level data.
 Examples -
Examples - political affiliation, religious affiliation,
blood type etc.
 Blood group types: AB, O, O, O, A , A, B,B,
A,O,O,O, A, B, B, B, B, AB, AB, B, A, B, B,B, AB,O,
O, O,.

Blood Type Frequency Distribution –
Blood Type Frequency Distribution – Example
Step 1: arrange data
Step 2: draw frequency table
Class Frequency Percent
A 5 20
B 7 28
O 9 36
AB 4 16

Ungrouped Frequency Distributions
Ungrouped Frequency Distributions
2. Ungrouped (discrete data) frequency
2. Ungrouped (discrete data) frequency
distributions -
distributions - can be used for data that can
be enumerated and when the range of
values in the data set is not large.

Examlpe:
 Frequency tables:
 Step 1. arrange data in ascending order tables
 Step 2. draw a frequency tables.
 For example: study of number of children in families.
 n= 30
 3, 2, 5, 3, 0, 1, 3, 2, 3, 4, 1, 3, 4, 5, 7,4, 1, 4, 5, 7, 2, 4,2,
0,8, 6, 5,4, 2,6.
 Step 1.
0,0,1,1,1,2,2,2,2,2,3,3,3,3,3,4,4,4,4,4,4,5,5,5,5,6,6,7,7,8.

 Step 2: draw table:
 Table (1) Title: # of children in families
# of
children
Frequency Relative
frequency
Cum.
frequenc
y
Cum.relati
ve
frequency
0 II 2 2/30=.07 2 2/30=0.067
1 III 3 3/30=0.1 5 5/30=0.167
2 IIIII 5 5/30=0.17 10 10/30=.33
3 IIIII 5 5/30=0.17 15 15/30=0.5
4 IIIII I 6 6/30=0.2 21 21/30=0.7
5 IIII 4 4/30=0.13 25 25/30=0.83
6 II 2 2/30=.07 27 27/30=0.9
7 II 2 2/30=.07 29 29/30=0.96
8 I 1 1/30=0.03 30 30/30=1.00
1

Grouped Frequency Distributions
Grouped Frequency Distributions
3. Continues data frequency distributions -
3. Continues data frequency distributions - can
be used when the range of values in the data
set is very large. The data must be grouped
into classes that are more than one unit in
width.

Terms Associated with a Grouped Frequency
Distribution
Distribution
 Class limits represent the smallest and largest
data values that can be included in a class.

distribution:
distribution:
The class boundaries
class boundaries are used to
separate the classes so that there are
no gaps in the frequency distribution.

Terms Associated with a Grouped
Terms Associated with a Grouped
The class width
class width for a class in a
frequency distribution is found by
subtracting the lower (or upper) class
limit of one class minus the lower (or
upper) class limit of the previous
class.

Guidelines for Constructing a Frequency
Guidelines for Constructing a Frequency
Distribution
Distribution
There should be between 5 and 20
classes.
The class width should be an odd
number.
The classes must be mutually
exclusive.

Guidelines for Constructing
Guidelines for Constructing
a Frequency Distribution
a Frequency Distribution
The class must be equal in width.

Procedure for Constructing a Grouped
 Find the highest and lowest value.
 Find the range.
 Select the number of classes desired.
 Find the width by dividing the range by the
number of classes and rounding up.

 Select a starting point (usually the lowest
value); add the width to get the lower
limits.
 Find the upper class limits.
 Find the boundaries.
 Tally the data, find the frequencies and
find the cumulative frequency.

Grouped Frequency Distribution -
Grouped Frequency Distribution -
Example
 In a survey of 20 patients who smoked,
the following data were obtained. Each
value represents the number of cigarettes
the patient smoked per day. Construct a
frequency distribution using six classes.
(The data is given on the next slide.)

10 8 6 14
22 13 17 19
11 9 18 14
13 12 15 15
5 11 16 11
2-2 Grouped Frequency Distribution -
Example

Example
 Step 1:
Step 1: Find the highest and lowest
values: H = 22 and L = 5.
 Step 2:
Step 2: Find the range:
R = H – L = 22 – 5 = 17.
 Step 3:
Step 3: Select the number of classes
desired. (In this case it is equal
to 6).

Example
 Step 4:
Step 4: Find the class width by
dividing the range by the number of
classes. Width = 17/6 = 2.83. This
value is rounded up to 3.

Example
 Step 5:
Step 5: Select a starting point for the
lowest class limit. For convenience,
this value is chosen to be 5, the
smallest data value. The lower class
limits will be 5, 8, 11, 14, 17 and 20.

Example
 Step 6:
Step 6: The upper class limits will be
7, 10, 13, 16, 19 and 22. For
example, the upper limit for the first
class is computed as 8 - 1, etc.

Example
 Step 7:
Step 7: Find the class boundaries by
subtracting 0.5 from each lower class
limit and adding 0.5 to the upper
class limit.

Class Limits Class Boundaries Frequency Cumulative Frequency
05 to 07 4.5 - 7.5 2 2
08 to 10 7.5 - 10.5 3 5
11 to 13 10.5 - 13.5 6 11
14 to 16 13.5 - 16.5 5 16
17 to 19 16.5 - 19.5 3 19
20 to 22 19.5 - 22.5 1 20
Note: The dash “-” represents “to”.

Frequency table (Continuous Data)
 Frequency of patient’s age with heart
disease, n = 30
 48.1,32,51,53,40,68,62,36.1,32,45,51,67,53,
59,47,63,52,64,61,43,56,58,66,54,56,52,40,55,
71,69
 Step 1; Arrange the data in ascending order.
 32,32,36.1,40,41,42,43,45,47,48.1,51,51,52,
53,53,54,55,56,56,58,59,61,62,63,64,66,67,
68,69,71
31

Frequency table (Continuous Data)
 Step 2; Range = X max – X min = 71 – 32 = 39
 Class intervals: Equal, non-overlapping sets.
 Number of intervals is taken intuitively about 5 – 15
 Width is taken according to medical importance of the
variable. ( in this example it is 5)
 We can calculate the number of class interval as follows.
 Number of intervals = range/ Width of class interval =
39/5~ 8
 No of intervals = 8
 We take Number of intervals as ‘8’ in this example.
32

Example
 Step 8:
Step 8: Tally the data, write the numerical values
for the tallies in the frequency column and find the
cumulative frequencies.
 The grouped frequency distribution is shown on
the next slide.

Frequency table
Class limits age
(years)
Frequency Relative
frequency
Cumulative
frequency
Cumulative relative
frequency
32 – 37 years 3 3/30 = 0.1 3 3/30 = 0.1
37 – 42 years 2 2/30 = 0.67 5 5/30 = 0.167
42 – 47 years 3 3/30 = 0.1 8 8/30 = 0.267
47 – 52 years 4 4/30 = 0.16 12 12/30 = 0.367
52 – 57 years 7 7/30 = 0.267 19 19/30 = 0.633
57 – 62 years 3 3/30 = 0.1 22 22/30 = 0.733
62 – 67 years 4 4/30 = 0.134 26 26/30 = 0.867
67 – 72 years 4 4/30 = 0.134 30 30/30 = 1.00
34

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Graphs
Graphs are Geometrical designs:
- Convey information at a glance

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Presentation
 Which type of chart?
 Data structure
 Variable type
 Measurement characteristics
 Questions to ask
 Type of data
 Qualitative
 Quantitative

37
Graphical Presentation of Qualitative
Data
 Sliding Bar Chart (e.g. Population Pyramid)
 Pie Chart
 Line chart

Bar chart:
 Convenient graphical device, particularly use for
displaying nominal and ordinal data e.g. data like sex,
ethnicity, educational level etc.
 The various categories are represented along
horizontal axis by making equally spaced vertical bars
i.e. rectangular areas.
 The heights of bars are proportional to values of items
for that category.
 The bar chart may have vertical or horizontal bar.
Three types of bar chart are….
1.Simple Bar chart
2.Multiple Bar chart
3.Component Bar Chart

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Simple BAR CHART
Sex
Female
Male
Frequency 80
70
60
50

40
re 2.2 Bar graph showing the number of students of each category

Bar chart
0
1
2
3
4
5
6
7
frequency
Frequencyof children in different families
Frequency
41

multiple/compound bar chart
 it is use when a number of items are to be
compared in respect of two or more values at a
time.
 For convenience bars are differently shaded.
 e.g. Ascites presence or absence in both gender.

43
MULTIPLE or compound BAR CHART (VERTICAL)
GENDER
Female
Male
ASCITES
60
50
40
30
20
10
Ascites
Yes
No

Component or proportional bar chart
 In a component bar chart, the bars are divided
into two or more.
 Each part represents a certain item and
proportional to the magnitude of that particular
item.

Pie chart/sector diagram:
 A pie chart is a circular chart divided into sectors,
illustrating numerical proportion. In a pie chart,
the arc length of each sector (and consequently
its central angle andarea), is proportional to the
quantity it represents. While it is named for its
resemblance to a pie which has been sliced, there
are variations on the way it can be presented.
 The name pie diagram is given to a circle diagram
because in determining circumference of a circle .
 Pie is represented as π.

Pie chart: Example
Body Mass Index
Frequency Percentage degree
Normal BMI
213 60.9 219.24
Above Normal BMI
137 39.1 140.7
Total
350 100.0 360

53
PIE CHART
Figure 2.3 Pie chart showing the number of students of
each category

10/10/24 54
Line Graph
A line graph is a graph
used to show change
over time!!
What can time be measured in???
Seconds - Minutes - Hours – Days -
Weeks - Months – Years - Decades -
Centuries - etc.

 A line chart or line graph is a type
of chart which displays information as a series of
data points called 'markers' connected by
straightline segments.
 It is a basic type of chart common in many
fields. It is similar to a scatter plot except that the
measurement points are ordered (typically by
their x-axis value) and joined with straight line
segments.
 A line chart is often used to visualize a trend in
data over intervals of time – a time series – thus
the line is often drawn chronologically. In these
cases they are known as run charts

 To draw the line chart, take the value of
independent variable on x- axis and value of
dependent on y-axis.
 If one of the variable is time then its values are
always taken on x-axis.
 With reference to x and y-axis the given data
may be plotted as point or dots on graph paper.
 These consecutive points or dots are then joined
by straight lines.

10/10/24 57
When to use a line graph?
Would we use a line graph
in the following situations:
•To show how many people like pizza in
this class? NO
•To show how many people live in East
Meadow? NO
•To show how much it rained each month
this year? YES- because months and years deal with time.

10/10/24 58
Money spent this week
$0.00
$5.00
$10.00
$15.00
$20.00
$25.00
Mon. Tues. Wed. Thurs. Fri.
Day
Amoutn
of
$

Tutorial-1
 A researcher is determining the average length of stay in
hours of Cesarean birth mothers in the hospital. He took
a sample of 15 mothers from the population and
determined the length of stay in hours. The data is as
follows.
 61.5, 70, 112, 74, 104, 97, 85, 132, 125, 70, 89, 94, 116,
67, 79.
 What type of data is this?
 Draw frequency table for this data?
59

Tutorial -2
 Data was collected from 15 security guards of
different schools regarding their education level.
 Primary : 3
 Middle: 5
 Metric: 5
 Above metric: 2
Show the best graphical presentation regarding
above data.

data presentation....................ppt

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