1.
COMMUNITY DENTISTRY
Dr Sachin Rathod
Email:- drsachin.rathod@yahoo.com
STATISTICS
2.
∗ Principle and method for the collection of
presentation ,analysis and interpretation of
numerical data of different kinds
∗ 1)observational data, quantitative data
∗ 2)data that have been obtained by a
repetitive operation
∗ 3)data affected to a marked degree of a
marked degree of a multiplicity of causes
DATA
3.
∗USES OF STATISTICS IN DENTAL SCINCES
ARE AS FOLLOWS:
∗ TO indicate the state of oral health in he
community and to determine the availability
and utilization of dental care facilities.
∗ To indicate the basic factor underlying the state
of oral health by diagnosing the community and
solution to such problem.
4.
∗To promote health legislation and
in creating administrative standards
for oral health.
∗To determine success or failure of
specific oral health care programs
or to evaluate the programmed
action.
5.
∗WHY STATISTIC
∗ While conducting and oral health examination the
investigator makes observation according to his
judgment of the situation. This depends on his skill,
knowledge, experience and temperament. Grading of
plaque score or malocclusion or the quantity of diet
are situation, which are influenced by the particular
investigator who makes the observations. If the same
observer repeat the observation on the same case
after some time lapse, he may or may not agree with
his previous assessment.
6.
Similarly if more than on
investigator observes the same
individual all of them may not
agree in their assessment. This
variability in measurement can be
handled using statistics.
7.
Data
∗ A collective recording of observation either
numerical or other wise its called data.
∗ These observation may be collected in a simple way
like recording the sex of person in a community or
noting down the number of cases of an oral disease
in a community or maybe done through an
experiment such as finding shear bond of
cementum.
8.
∗VARIABLE
∗A certain observation is made of
characteristic which varies from
one person to the other person
is called variable
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∗ TYPES OF DATA ON THE BASIS OF NATURE OF
VARIABLE
∗ QUALITATIVE DATA: When data is collected on the
basis of attributes or qualities like sex, malocclusion,
cavity etc is called qualitative data.
∗ QUANTITATIVE DATA: when the data is collected
through measurement using calipers like arc length arc
width fluoride concentration in water supply etc. is
called quantitative data.
∗ Quantitative data can be classified in 2 kinds as
DISCRETE AND CONTINUOUS
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∗DISCRETE: When the variable under
observation takes only fixed value like
whole numbers, the data is discrete e.g.
the DMF teeth
∗CONTINUOUS DATA: If the data can
take any value in a given range, decimal
or fractional is called continuous data
like arc length
11.
∗SOURCES OF DATA ARE:
∗ SURVEYS
∗ EXPERIMENTS
∗ RECORDS IN OPD OF DENTAL CLINICS
∗ DATA CAN BE COLLECTED EITHER THROUGH
∗ PRIMARY SOURCE
∗ SECONDRY SOURCE
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∗PRIMARY SOURCE: The data is obtained
directly by the investigator himself. This
is first hand information
∗SECONDARY SOURCE: The data is
already recorded to serve the purpose
of the objective of the study. e.g. the
record of opd of dental clinics.
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∗Primary data can be obtained using
anyone of the following methods
∗Direct personal interview
∗Oral health examination
∗Questionnaire method
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∗ DIRECT PERSONAL INTERVIEWS
∗ In this method there is face to face contact with
the person from whom the information is to be
obtained (called as informants) this method
enables to measure subjective phenomena such
as the oral health status the opinions, beliefs and
attitudes and some behaviourial characteristics.
15.
∗The advantage of this method is that all
the information can be collected
accurately and any ambiguity can be
clarified. Thus method can not be used
when the study is extensive because it
is a time consuming and require more
personal.
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∗ ORAL HEALTH EXAMINATION:
∗ When information is needed on the oral disease,
this method provides the more valid information
than health interview.
∗ QUESTIONNAIRE METHOD:
∗ In this method, a list of question pertaining to
the survey-known as questionnaire is prepared
and the varies informants are requested to
supply information either personally or through
past.
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∗The question should be short easy to
understand. There should be no
ambiguity while answering the
question.
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∗ POPULATION
∗ The group of all individual who are the focus of
the investigation is known as population. e.g. if it
decided to get the prevalence of the DMF teeth
in school children then all the children of the
school form the population.
∗ CENSUS ENUMERATION
∗ If the information is obtained from each n every
individual in the population then it is called
census enumeration.
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∗ SAMPLE
∗ The word sample means the group of individual who
are actually available for the investigation. The sample
is the portion of population selected from a population
in some manner.
∗ Aim of sample is to get information on a larger group or
population. The logical first step in any study is to
define population of interest. (target population)
∗ The next step is to list all the individual in that
population as a prelude to select a sample for a detail
study.
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∗SAMPLING UNITS
∗The individual entities that from the focus
of study are termed as sampling units.
∗SAMPLING FRAME
∗The list of sampling unit is known as
sampling frame.
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∗ Sample selection can be done in two
ways :
1) Purposive selection: The selection of a
sample primarily aims at representing
the population as a whole. Hence, there
can be a great temptation to
deliberately or purposively select the
individual who seems to represent the
population under study
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2) Random selection: Here a sample of unit is
selected in such a way that all the characteristic of
the population is reflected in the sample . This is
possible by the selecting unit of sample at random
APPILICATION OF SAMPLING IN COMMUNITY
DENTISTRY ARE:
A evaluation of oral health status of a community
B evaluation of health education on oral hygine
C studies on administrative aspect of the service like
availability and utilization of oral health facilities in
the community.
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SAMPLING DESIGN
Different sampling design are available depending
upon the type and nature of the population and
the objectives of the investigations. Some design
commonly used are :
(a) Simple random sampling
(b) Systemic random sampling
(c) Stratified random sampling
(d) Cluster random sampling
(e) Multiphase sampling
(f) Path finder survey
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∗ SIMPLE RANDOM SAMPLING
∗ This is a sampling technique in which each n every
unit in the population has an equal chance of being
included in the sample. In this method the selection
of unit is determined by chance only
∗ (a) Lottery method
∗ (b) Table of random number
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∗(b) SYSTEMIC RANDOM SAMPLING
∗A systemic sample is formed by
selecting one unit at random and than
selecting additional unit at evenly
spaced interval till the sample of
required size has been formed. This
method is used when a complete list of
population is available.
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∗ (C) STRATIFIED RANDOM SAMPLING
∗ The population to be sample is sub divided into
groups known as strata, such that each group is
homogeneous in its characteristic.
∗ A simple random is than chosen from each stratum
this type of sampling is used when the population is
heterogeneous with regard to the characteristic
under study.
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∗ (D) CLUSTER SAMPLING
∗ This method is used when the population forms
natural group or cluster such as village, children of
school here first a sample of the cluster is selected
and then all the unit each of the selected cluster are
surveyed.
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∗ (E) MULTIPHASE SAMPLING
∗ This method a part of information is collected from
the whole sample and a part from the sub-sample.
∗ (F) PATH FINDER SURVEY
Some time there is need to sample a specified
proportion of the population say 1% in order to
estimate disease prevalence accurately,
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∗This method used is a stratified cluster
sampling technique which include the
most important population subgroups
like to have differing disease level and
to cover a standard number of subjects
in specific index age group in this way
statistically significant and clinically
relevant information for planning is
obtained of at minimum experience.
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∗This method is suitable for the following
situation.
∗1. The over all prevalence of the various
oral disease affecting the population.
∗2. Important variation in disease level
severity and need for treatment
subgroups of the population this
enables groups in special needs of high
priority development of science to be
identified.
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∗ SAMPLE SIZE
∗ A common question while condecting an
investigation is about the size of the sample
because the sample higher will be the precision of
the estimates of the sample is to be considered
keeping in mind the following factor.
∗ 1. An approximate idea of the estimates of the
characteristic under study and its variability from
unit to unit in the population. This may be obtained
from previous investigation conducted immediately
before the start of actual investigation.
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2. Knowledge about the precision of the estimates of
the characteristic.
3.The probability level with in which the desired
precision is to be maintained..
4.The availability of experimental material, resources
and other practical consideration.
For instance in a filed survey is to be conducted to
estimate the prevalence rate of a disease the
sample size is calculated by the formula-
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Where n is the sample size, p
approximate prevalence rate of
disease ,l is the permissible error in
the estimation of p and za is the
normal value for the probability
level
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∗ ERROR IN SAMPLING
∗ Sampling error occurs due to
∗ (A) Faulty sampling design
∗ (B) Small size of sample
∗ Non sampling error
∗ (A) Coverage error: due to non response or non
corporation of the informant
∗ (B) Observational error: due to interviewer bias or
imperfect experimental technique.
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∗ Processing error: due to error in statistical
analysis
∗ PRESENTATION OF DATA
∗ There are two main categories of
presentation of data
∗ (a) Tabulation
∗ (b) Diagram
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∗ Tabulation:
∗ Broadly, the data can be classified on the
following bases:
∗ (a) geographical, i.e., area wise, e.g. cities,
districts
∗ (b) chronological, i.e., on the basis of time
∗ (c) qualitative, i.e., according to some
attribute
∗ (d) quantitative, i.e., in terms of magnitude
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∗ The two element of classification are:
∗ (a) frequency
∗ (b) variable
∗ Frequency is the number of units belonging to each
group of variable. A commonest way of presenting
data in the table is known as frequency distribution
table. The variable characteristic such as age, arch
dimension, fluoride concentration in water supply
has a range from lowest to highest. This range is
divided into subgroup called classes.The class limits
are the lowest and highest value that can be
included in the class
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∗ While forming a frequency distribution table
the following basic rules are to be followed
∗ (a) Every table should contain a little as to
what is depicted in the table
∗ (b) The number of classes intervals should
be too many or too less. It may be preferably
between 5 and 20
∗ (c) The class interval should be at equal
width
∗ (d) Unit of measurement should be specified
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∗The class limit should be clearly defined
to avoid ambiguity. for e.g. 0-4, 5-9,10-
14,etc.
∗Each row and column should be clearly
defined with the heading for each row
and column.
40.
∗ (B) DIAGRAMS
∗ By arranging the data into tables, we simplify the
entire mass of data. But sometimes it is difficult to
understand and compare two or more tables .
Diagrams and graphs are one of the most
convincing and appealing ways of depicting
statistical results. diagrams and graphs are
extremely useful because they are attractive to
eyes, have lasting impression on the mind of the
layman and they facilitate comparison of data
relating to different time periods and region
41.
TYPES OF DIAGRAMS
Depending on the nature of data, whether it is
qualitative or quantitative, any one of the
following diagram may be chosen :
(a) Bar diagram: this diagram is used to represent
qualitative data. It represent only one variable.
For example, the number of the people with
D,M,F teeth in a particular age group may be
shown by a bar diagram
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∗ ILLUSTRATION: Following table gives the D,M , F ,and teeth
for individuals aged 15-24 years.
∗ Tooth status No. of individuals
∗ D 10
∗ M 18
∗ F 12
∗ DMF 10
43.
∗ (b) MULTIPLE BAR:
∗ This diagram is used to compare qualitative data
with respect to a single variable, like sex wise or
with respect to time or region.
∗ Illustration 2
∗ YEAR Rural URBAN
∗ 1994 124 87
∗ 1995 109 72
∗ 1996 97 70
∗ TOTAL 330 229
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∗ (c) Proportional bar diagram:
∗ This diagram use to represent qualitative
data when it is desired to compare only the
proportion of subgroup between different
major group of observation. The bars are
drawn for each group with the same length
either as 1% or 100% . These are then divided
according to the subgroup proportion in
each major group.
45.
∗(D) Pie diagram:
∗These are popularly used to show
percentage breakdown for qualitative
data. It is so called because the entire
graph look like a pie and its component
represent slices cut from a pie. A circle is
divided into different sector
corresponding to the frequency of the
variable in the distribution.
46.
∗ (E) component bar diagram:
∗
∗ This diagram is used to represent qualitative
data. When it is desire to represent both the
number of cases major groups as well as
subgroups simultaneously we use the
component bar diagram. First we draw the
rectangle proportional to the number of
cases of major group then each rectangle Is
divided into the subgroups.
47.
∗(F) Line diagram
∗This diagram is use to study changes of
value in the variable over time and is the
simplest type of diagram on the X axis
the time such as hours, days, weeks,
months, years are represented in the
value of any quantity pertaining to this
is represent along Y axis
48.
∗ Following are the number of patient at the OPD of dental
clinic for one year:
∗ year no. of patient in OPD
∗ 1983 554
∗ 1984 580
∗ 1985 560
∗ 1986 604
∗ 1987 500
∗ 1988 300
∗ 1989 230
49.
∗(G) Histogram
∗This diagram use to depict quantitative
data of continuous type. Histogram is a
bar diagram without gape between the
bars. It represent the frequency
distribution.
50.
following is the frequency distribution of fluoride
concentration in parts per million for the water supply of 25
communities.
class interval frequency
0.2-0.3 1
0.4-0.5 1
0.6-0.7 1
0.8-0.9 5
1.0-1.1 10
1.2-1.3 4
total 22
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∗(H) Frequency polygon:
∗This is used to represent frequency
distribution of qualitative data and it is
used to compare two or more
frequency distribution.
52.
∗(I) CATOGRAMS OR SPOT MAP:
∗These are used to show
geographical distribution of
frequencies of a characteristic.
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COMMUNITY DENTISTRY
Dr Sachin Rathod
Email:- drsachin.rathod@yahoo.com
Thank you
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