random sampling method
TRANSCRIPT
-
8/12/2019 Random Sampling Method
1/15
PROBABILITY SAMPLING (RANDOM)
Simple Random sampling
Systematic sampling
Stratified sampling
Cluster sampling
ProbabilitySampling
A method of sampling that uses of randomselection so that each member of the
population, or of sub-groups, has an equal
probability of being chosen.
-
8/12/2019 Random Sampling Method
2/15
Definetarget
population
Identifysampling
frame
Determinesample
size
Determinemethod ofsampling
Selectsample
Steps in probability sampling
Step 1 Step 2 Step 3 Step 4 Step 5
-
8/12/2019 Random Sampling Method
3/15
1.Simple Random Sampling (SRS)In a SRS, subjects are selected from the population in
which every member of the population has equal chanceof being chosen (e.g., drawing names out of a hat, use atable of random number). Applicable when population issmall, homogeneous & readily available.
-
8/12/2019 Random Sampling Method
4/15
Systematic Sampling is a sampling method in which
every nth elementis selected from a list of all elements
in the survey population, beginning with a randomly
selected element.
E.g, from among 50 students, we need to select 5 to be
our sample (10%), we would randomly select a number
from 1 to 10, then select every 10thstudent for our
sample.
2. SystematicSampling
-
8/12/2019 Random Sampling Method
5/15
-
8/12/2019 Random Sampling Method
6/15
A population is divided into homogenous, mutually
exclusive starta or subgroups (age, gender, location,level of education), and a sample is randomly selected
from each stratum.
3. Stratified (Random) Sampling
Proportionate stratified
sampling
based on the
percentage of subjectsin the population that is
present in each stratum.
Disproportionate stratified
sampling
the researcher selects the
same number of subjectsto be in each stratum of
the sample.
-
8/12/2019 Random Sampling Method
7/15
-
8/12/2019 Random Sampling Method
8/15
-
8/12/2019 Random Sampling Method
9/15
-
8/12/2019 Random Sampling Method
10/15
Section 4
Section 5
Section 3
Section 2Section 1
-
8/12/2019 Random Sampling Method
11/15
is the selectionof two or more levelsof clusters.
E.g., school districts, schools within districts,
classroom within school, students within
classroom. We could begin by sampling 40 of
150 school districts, then 6 classrooms in each
of the 40 districts, and then 10 students in
each classroom.
Multi-stage cluster Sampling
-
8/12/2019 Random Sampling Method
12/15
STRENGTHS AND WEAKNESSES OF SAMPLING METHOD
Sampling
methods
Advantages Disadvantages
Simple
Random
Sampling
Easy to understand
Little knowledge of
population needed.
Free of subject
classsification error
Easy to analyze and
interpret results.
Require numbering
each element in a
non-electronic list of
members of the
population.
Larger sampling
error than in
stratified sampling
for same sample size.
-
8/12/2019 Random Sampling Method
13/15
Sampling Advantages Disadvantages
Systematic(Random)
Sampling
Easier to draw.Easy to
understand
Free of subject
classsification error.Easy to analyze
and interpret
results.
Subjects dont
need to be
numbered.
Largersampling error
than in stratified
sampling for
same samplesize.
Periodicty in
list of population
elements.
-
8/12/2019 Random Sampling Method
14/15
Sampling
Techniques
Advantages Disadvantages
Stratified
(Random)
Sampling
Allow easy subgroup
comparisons.
More representativethan Simple random or
systematic.
Fewer subjects
needed if strata arerelated to the
dependent variable.
Requires
subgroup
identification ofeach population
element.
Costly and
difficult toprepare lists of
population
elements in each
subgroup
Advantages & Disadvantages
-
8/12/2019 Random Sampling Method
15/15