BIOSTATISTICS
7/21/20161
(part-1)BIOSTATISTICS7/21/20162
Date-21/07/2016Topic Biostatistics (part-1)Duration 40
minutesSubject Public Health Dentistry Time Of Class
3.00-4.00pmTarget audience final year B.D.S studentsMethod of
presentation PowerPoint presentationAudio & Visual Aids Used
LCD Projector & LaptopObjectives- By the end of the class,
students should understand the method of data presentation and
types of sampling,Method of evaluation- by asking questions at the
end of the class
7/21/20163
Lesson planTopic: Biostatistics part-1Year: B.D.S VI yearDate:
21/07/2016Time: 3:00 pm -4:00 pmSetting: Aim: to teach about the
method of data presentation and types of sampling.Learning
objectives: The students should learn about the method of data
presentation and types of samplingSl . No.CONTENTTL MethodsTL
MediaTime1.Introduction LecturePower point10 mins2.-Presentation of
data. LecturePower point20 mins3.Sampling techniques . LecturePower
point20 mins4.Sampling ErrorLecturePower point15 mins.5.Non
SamplingDiscussion Power point10mins
7/21/20164
Contents:-IntroductionPresentation of data - Methods of
presentation Data.Sampling techniques Sampling ErrorNon Sampling
errorReferences
7/21/20165
INTRODUCTIONThe word Statistics is derived from Latin for state
indicating historical importance of data gathering, which
principally is demographic information. Statistics is the science,
which deals with collection, organization, summarization, analysis,
interpretation and presentation of data.Inferences derived from
these findings help in making valid decisions. Statistical methods
and techniques applied to biological problems or data is called
Biostatistics. 7/21/20166
Presentation of DataWhat is Data?-facts and statistics collected
together for reference or analysis.Data collected from various
experiments.It should be compiled, classified and presented in a
purposive manner to bring out important points.7/21/20167
Methods of Presentation of Data.Based on the data type,
representation of data also differs.There are two different types
of data in statistics; they are; discrete, and continuous type of
data.Discrete data are distinct and separate and also invariably
whole numbers. eg. Number of deaths due to particular diseases.
7/21/20168
Continuous data are those, which takes the value between range
of values, eg height, weight, age.There are two methods of
presenting the data:-TabulationCharts and diagrams
7/21/20169
Tabulation (frequency distribution table):- The distribution of
the total no. of observation among the various categories is termed
as a frequency distribution. 7/21/201610
7/21/201611
Charts and diagrams:- Presenting data in these forms is useful
in simplifying the presentation and enhancing comprehension of the
data. Representation of data in these form provides the
following:-
7/21/201612
7/21/201613
Bar chart:-These are the way of presenting a set of numbers by
length of a bar; the length of the bar is proportional to the
magnitude to be represented.Bar charts are easy to prepare, easy to
understand and enable visual comparison. There are three types of
bar charts:-Simple bar chart Multiple bar chartComponent bar
charts
FOR DISCRETE DATA7/21/201614
7/21/201615
7/21/201616
7/21/201617
Component bar graph showing male and female ratio
2. Pie chart:-In these diagrams the areas of segments of a
circle are compared. The area of each segment depends upon the
percentage, which is converted to angle and drawn.7/21/201618
7/21/201619
Pie chart
3. Pictogram:-These diagrams are used for a layman those who
cannot understand technical charts like bar charts.Here pictures
and symbols are used to present the data.7/21/201620
7/21/201621
Histogram:- Histogram is a set of vertical bars whose areas are
proportional to the frequencies represented.The class intervals are
given along the horizontal axis and the frequencies along the
vertical axis.
FOR CONTINUOUS DATA7/21/201622
7/21/201623
2. Line charts:-It shows trends or changes in data varying with
a constant, at even intervals.A line chart emphasizes the flow of a
constant and rate of change, rather than amount of change.When we
need to show trends or changes in data at uneven or clustered
intervals, an XY (scatter) chart is used.7/21/201624
7/21/201625
3. Frequency curve:-A frequency polygon is a graphical display
of a frequency table. The intervals are shown on the x-axis and the
number of the scores in each interval is represented by the height
of a point located above the middle of the interval.The points are
connected so that together with the X-axis they form a polygon.
7/21/201626
7/21/201627
SAMPLING TECHNIQUESThe study population is too large and it may
be too expensive or too time consuming to attempt either a complete
or nearly complete coverage in a statistical study, so we take a
sample from the population.Sample is the representative of the
population and to ensure that we chose each unit of the sample
technically. This process is called sampling technique.Sufficient
sample size is calculated based on the proportion of and precision
required. 7/21/201628
There are two methods in sampling techniques:-7/21/201629
Simple random samplingIt is applicable when:-The population is
small.The population is available the population is homogenous.This
is done either by using random table or lottery method. The
principle used to select the sample is each and every unit will
have equal chance of getting selected.7/21/201630
Systematic samplingThis technique is applicable when:-The
population is large and scattered but the population list available
(sampling frame), and The population is not homogeneous.The
principle used in selecting the sample is every kth unit of
population is selected, where K is sampling interval, which is
calculated as:
Sample interval (k)= Total population/sample size7/21/201631
This technique leads to more accurate result if the population
is homogenous.7/21/201632
Stratified samplingThis sampling technique is applicable
when:-The population is large.The population is not
homogenous.First the population is divided into homogenous group
called strata, and the sample is drawn from each stratum at random
in proportion to its size.This gives greater accuracy result.The
demerit of this technique is, dividing the population into
homogenous group.7/21/201633
7/21/201634
Cluster sampling.Cluster sampling is applicable when preparing
the sampling frame is difficult. In it, geographical area is
divided into small area called cluster.This technique allows only
small number of target population to be sampled. Normally 30
clusters are selected by systematic sampling method.Error will be
more but cost of study is reduced.7/21/201635
7/21/201636
Judgment Choosing the sample items depends on the judgment of
the investigator.Samples are because the investigator believes that
they are typical or representative of the population under his/her
study.7/21/201637
Convenience samplingSelection is made from an available source
like that from a nearly college students to study the awareness
regarding AIDS in college students, because getting sample is
convenient. Non- random sampling is biased and unsatisfactory, but
time, cost and resource required will be considerably
less.7/21/201638
7/21/201639
Quota Sampling7/21/201640The general composition of the sample
is decided in advance. The only requirement is that to find right
number of people to somehow fill the quotas. This is generally done
to insure the inclusion of a particular segment of the
population.
Purposive Sampling7/21/201641A purposive sample is a
non-representative subset of some larger population, and is
constructed to serve a very specific need or purpose..A subset of a
purposive sample is a snowball sample (chain referral sampling) so
named because one picks up the sample along the way, analogous to
snow ball accumulating. snow.A snowball samples is achieved by
asking a participant to suggest some one else who might be willing
or appropriate for the study.
SAMPLING ERRORThe occurrence of variation from one sample to
another sample is called sampling error.The factors that influence
the sampling error are:Size of the sample.Natural variability of
the individual reading.As the size of the sample increases,
sampling error will decrease.7/21/201642
NON-SAMPLING ERRORSampling error is not only error which arises
in a sample survey, error may also occur due to inadequately
calibrated instruments. 7/21/201643
REFERENCES 7/21/201644Hiremath SS. Textbook of preventive and
community dentistry. 2nd edition, 2011. Elseviers Publications.
Peter S. Essentials Of Preventive And Community Dentistry.5TH nd
Edition,2014. Arya publications.
7/21/201645
