BIOSTATISTICS

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					BIOSTATISTICS
STATISTICS
  It is the scientific study of collection,
  organization,analysis and interpretation of
  data.
• Descriptive / Inferential

BIOSTATISTICS
  It is the application of statistical principles
  for evaluation of biological studies or
  problems.
• Importance
          APPLICATIONS
• Clinical Medicine   • Environmental
• Biological Lab        Health
  Research            • Health Services
• Biological Field    • Wildlife Biology
  Research            • Agriculture
• Genetics            • Fisheries
• Ecology             • Epidemiological
                        Studies
POPULATION (TARGET POPULATION)
 Total number of observations about which the
 inference is to be drawn. A population is an
 aggregate of creatures, things, cases and so on.
SAMPLE
 A collection of individual observations selected
 from population by a specified procedure.
SAMPLING
PROBABILITY / NON- PROBABILITY
RANDOMIZATION
SAMPLE SIZE
ADVANTADES
BIAS
Error that leads to an incorrect conclusion.
• Sampling / Data collection / Analysis /
  Interpretation of results
ATTRIBUTE
Character or a quality that a person may have.
• Categories – tall / short
VARIABLE
Measured characteristic of a person, object or
  phenomenon in a study that can give different
  values in different subjects.
• Example – height measured
• Dependent / Independent / Confounding
PLACEBO
It is a dummy drug that is devoid of
 pharmacological activity but acts by
 psychological suggestions. It is an inert
 material with exactly same appearance,
 colour, consistency, etc. as the active
 dosage form under study.
PLACEBO RESPONSE
           CLINICAL TRIAL
A controlled & ethically designed experiment
  on human beings with aim of answering
  some precisely framed questions or to
  investigate the efficacy of some medical
  treatment.
• Design / Correlation / Analysis / Conclusion
METHODS
• Open trial
• Single blind trial
• Double blind trial
• Cross over trial
DATA
The set of observations of an experiment, census or
   a sample survey on which the analysis is carried
   out.
TYPES
1. Quantitative / Numerical          INFORMATION
  1. Continuous – age, BP
  2. Discrete – no. of indoor patients
2. Qualitative / Categorical
  1. Ordinal – Ranking in class
  2. Nominal – Blood gps, Marital status
DESCRIPTION / PRESENTATION
         OF DATA
• Tables
• Charts
• Diagrams
• Graphs
• Pictures
           TABULATION
• Characteristics
 Numbering / Title / Headings / Order of
 data / foot notes
• Simple table
• Frequency distribution table
• Frequency distribution or Frequency
  distribution table is a description of data
  presented in tabular form so that data will
  be more manageable. It gives the
  frequency (or the number of times) with
  which a particular value appears in the
  data
• Tabulation
• Arrangement of data in ascending order
• Calculation of different frequencies
Systolic B.P of female students(n=10)
       RAW DATA       ARRANGED IN
                     ASCENDING ORDER
  1      110             100
  2      115             105
  3      110             105
  4      100             110
  5      105             110
  6      110             110
  7      115             110
  8      105             115
  9      110             115
  10     120             120
• Absolute F. (v) – no. of observations fall
                        into each class
• Relative F. – v / n
• Percentage F. – v / n x 100 (RF x 100)
• Cumulative F. – no. of absolute freq.
 cumulatively added until all are accounted
                                       for.
B.P      Absolut Relative     Percent Cumulat
(mmHg)   e Freq(v) Freq       Freq =    -ive Freq
                   ( v / n)   v/n x 100


 100        1        0.1        10%        1

 105        2        0.2        20%        3

 110        4        0.4        40%        7

 115        2        0.2        20%        9


 120        1        0.1        10%       10
  Charts / Graphs / Diagrams
• Bar chart
• Histogram
• Frequency polygon
• Line chart / diagram
• Pie chart / diagram
• Pictogram
             BAR CHART




Simple Bar   Multiple Bar   Component
   Chart       Chart         Bar Chart
Simple Bar Chart
Multiple Bar Chart
Component Bar Chart
                 Histogram
• Pictorial diagram of
  frequency
  distribution.
• Consists of series of
  blocks or bars.
• The area of each
  block is proportional
  to the frequency.
• Distribution
 – Symmetrical
 – Skewed
          Frequency Polygon
• Diagramatic
  representation of
  a frequency
  distribution.
• Obtained by
  joining the mid
  points of bars in
  histogram.
Line Chart / Diagram
          Pie Chart / Diagram
• Area of segments
  of a circle are
  compared.
• Area of each
  segment depends
  upon the angle.
• Often necessary
  to indicate the
  percentages of
  segments as it
  may be difficult to
  compare the areas
  of segments.
                Pictogram

• Small pictures or
  symbols are
  used to present
  the data.
     CENTRAL TENDENCIES
• Central tendency of a set of observations
MEAN
• Arithmetic mean
• Average of the group
• Summing all the values for the subjects in
  the group and dividing by the number of
  subjects in the group.
       Mean = Sum of all the values / n
             X=Sx/n
X=mean, x=individual value, n=no. of
                               observations
MEDIAN
• The median is the middle value when
  observations are arranged in an order.
• The median represents the exact middle
  of a distribution.
• Odd / Even number of observations


MODE
• most frequently occurring data point
               EXAMPLE
• Consider weight of 10 individuals
   83, 75, 81, 79, 71, 95, 75, 77, 84, 90
• Arrange data in ascending order
   71, 75, 75, 77, 79, 81, 83, 84, 90, 95
• Mean = 810 / 10 = 81
• Median = 79 + 81 / 2 = 80
• Mode = 75
 MEASURE OF SPREAD / DISPERSION
• Variation is the spread or dispersion of a
  set of observations around some central
  value.
• Measure of dispersion estimates the
  variability of a distribution around the
  centre.
• Different Measures
  – Range
  – Variance
  – Standard Deviation (SD)
  – Coefficient of variation (C.V)
RANGE
• Difference between the lowest and highest
  value in the data set
• More variable data – Larger range
• Poor parameter – outliers
METHOD
• Find the range of the following data:
  29, 31, 24, 29,30, 25
• Arrange the data from smallest to largest:
  24, 25, 29, 29, 30, 31
• Identify the minimum and maximum values:
  Minimum = 24, Maximum = 31
• Range = 31-24 = 7
            Problem Solving
• Fasting blood sugar levels were measured in a
  group of 10 adult male subjects. The data is
  given below. Calculate

• Frequency distribution

• Central tendency measurement

• Range
DATA
  110, 105, 80, 90, 85, 120, 95, 105, 90, 105
Blood sugar Level of adult male subjects
     RAW DATA         ARRANGED IN
                     ASCENDING ORDER
1      110                 80
2      105                 85
3       80                 90
4       90                 90
5       85                 95
6      120                105
7       95                105
8      105                105
9       90                110
10     105                120
Blood sugar level of adult male subjects
B.P      Absolut     Relative   Percent     Cumulat
(mmHg)   e Freq(v)   Freq       Freq =      -ive Freq
                     ( v / n)   v/n x 100

  80         1         0.1        10%         1

  85         1         0.1         10%        2

  90         2         0.2         20%        4

  95         1         0.1         10%        5

  105        3         0.3         30%        8

  110        1         0.1         10%        9

  120        1         0.1         10%        10
• Mean = 985 / 10 = 98.5

• Mode = 105

• Median = 95 + 105 = 200 / 2 = 100

• Range = 120 – 80 = 40

				
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posted:3/8/2011
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