Statistical Methods in Biology
(Lecture)
Statistics- is a branch of science which deals with
the collection, presentation and analysis,
an interpretation of quantitative data.
Collection of Data
Population
- the total units under investigation
- set of data that consists of all hypothetically
possible observation of a certain phenomenon.
*Experimental Design (Definite)
A.
B. Sample
- part of the population
- set of data that contains only a part of the
total observations.
C. Census
- method of collecting data of a population
General Methods of Sampling
A. Probability Sampling
- all elements are given the chance to be
selected as a sample.
B. Non-probability Sampling
- not all elements are given the chance to be
selected as a sample.
Common methods of drawing probability samples
A. Simple Random Sampling
B. Systematic Sampling - makes a constant
Interval.
- needs a frame or list
- compute for the sampling interval
- pick the first sample at random
1st sample
=7
2nd sample
= 7+10
3rd sample
= 7 + 2 (10)
4th sample
= 7 + 3 (10)
50th sample
= 7 + 49 (10)
= 17
= 27
= 37
= 497
D. Sampling (Sample Survey)
- method of collecting data from samples
E. Parameter
- value taken from population data (Result)
F.
1.
2.
3.
4.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Statistic
- value taken from a sample data (Estimator of
a parameter)
Advantages of Sampling over Census
Reduced Cost
Greater Speed
Greater Scope
Greater Accuracy
Principal Steps in a Sample Survey
Formulate the objective of the survey
Define the population to be sampled
Identify the data to be connected
Specify the degree of precision desired (95%
or 99%).
Choose the instrument to be used
Construct a list of sampling units or frame
Select for an appropriate size of sample.
Conduct a pre-test
Organization of field work
Summary and analysis of data
Record information gained for future use
01 / 22 / 19
Use SI = 13
1st sample
= 11
2nd sample
= 11 + 13
= 24
5th sample
= 11 + 4 (13) = 64
last sample
= 11 + 99 (13) =1298
- non-probability sampling since not all elements
were given the chance to be selected as a
sample.
- identify the effect
- increase sample size only
Use SI = 13
1st sample
2nd sample
last sample
99th sample
98th sample
*kulang 2
= 12
= 12 +13
= 12 + 99 (13)
= 12 + 98 (13)
= 12 + 97 (13)
= 25
= 1299
= 1286
= 1273
C. Stratified Sampling - pick sample from every
(barangay); homogenous groups
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
*equal (n=90; probability proportionate to size
D. Cluster Sampling - heterogenous (pili la o
usa la); iba-iba it population or sample size
1
2
3
4
5
6
7
8
9
Common Non-Probability Sampling
1. Purposive Sampling
2. Convenience Sampling
3. Quota Sampling
01 / 25 / 19