Probablistic sampling group 3 assighnment
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Transcript of Probablistic sampling group 3 assighnment
A Group Assignment on Probabilistic Sampling For
Business Research Methods Course Requirement
By Section Two Group 3 Members
5-2
Group Member’s
1. Sara Jemal 2. Shimelis Birhanu 3. Setegn Addisu 4. Selamawit Wolde 5. Solomon T/Markos 6. Sisay Tufa
Course Instructor Dr. Shimelis Z.
Feb12.2017
Addis Ababa/ Ethiopia
PROBABILISTIC
SAMPLING
General Background
Sampling
Sampling Terminologies
Types Of Sampling
Types Probabilistic
Sampling
1. Simple Random Sampling
2. Systematic Random Sampling
3. Cluster Sampling
4. Stratified Sampling
5. Multi Stage Sampling
Summary on Selection
charts of Probabilistic
Sampling ?
1. Define basic sampling terminologies & Probabilistic Sampling.
2. Describe and discuss the different Probabilistic sampling
designs.
3. Discuss the factors to be taken into consideration for
determining types of Probabilistic Sampling.
4. Discuss the merit & a limitation of each Probabilistic Sampling
design.
5. To assist our colleague’s in order to utilize the concepts of
Probabilistic Sampling in there future projects Plan
Sampling method: is the process of selecting a small group to
representative the whole universe in order to:
obtain accurate info. with minimum cost, time & energy
To improve accuracy of such estimates
Probability sampling : Every item of the universe has an
equal chance/ Same probabilities of being included in the
sample.
Probability sampling AKA
Equal probability of selection (EPS) design.
self-weighting design.
Chance sampling or
Random sampling
Why Probability sampling Considered
we can measure the errors of estimation
we can measure the significance of results
It ensures the law of Statistical regularity
Population: collection of all elements in universe
Sample: is a subset of the population
Sampling: process used to determine the sample
Sampling units: collections of elements from the
population that cover the entire population
Sampling frame is a list of sampling units
Clusters: a group of similar things or people positioned or
occurring closely together.
Strata: an elements of homogeneous subgroups
Heterogeneous: is the state of being dissimilar.
Homogeneous: as the state of being similar.
• Achieving a representative sample • Minimizing sampling bias • Making statistical inferences • Less knowledge of universe is sufficient. • Sample representative of population
A) Advantages of Probability
Sampling
• It takes time • It is costly • Chances of selecting specific class of
samples only
B) Limitation of Probability
Sampling
1.5.1 Simple Random Sampling
The purest form of probability sampling & EPS design
It used when the population of interest is
Small, homogeneous & readily available
If our sampling frame has a periodic pattern
1 .5.1 Simple Random Sampling Cont.…..
A. Tossing a coin
B. Throwing a dice
C. Lottery method
D. Blind folded method
E. Random number table
F. Random number generation
A. SRSWR
SRS with replacement
AKA Equal probability SRS
B. SRSWOR
SRS without replacement
AKA Varying probability SRS
Types of SRS Techniques for Randomization
Step 3
Drawn the sample
Step 2
Prepare an exhaustive list (sampling frame) of all
member of the population
Step 1
Determine Types & Techniques of Randomization
1 .5.1 Simple Random Sampling Cont.…..
1. Easy to implement
2. Free from subjectivity & personal error.
3. Requires the minimum knowledge of population
4. provides appropriate data for one’s purpose.
5. can be used for inferential purpose
A. Imprecise for heterogeneous
B. It does not use the knowledge about the population
C. Cannot ensure the representativeness
D. Time taking & costly procedures
E. Its inferential accuracy depends upon the size of the sample
F. Can be disruptive to isolate members from a group
Advantages of SRS Limitation of SRS
Systematic Random Sampling:
It involves you selecting the sample at regular intervals from the
sampling
Each element has an equal probability of selection, but
combinations of elements have different probabilities.
It requires the complete information about the population.
There should be a list of information of all the individuals of the
population in any systematic way.
1.5.2 Systematic Random Sampling
When to Use Systematic Random Sampling?
1. When no list of population exists
2. When the list is roughly of random order
3. Small area/population
1.5.2 Systematic Random Sampling
1.5.2 Systematic Random Sampling Procedures
Step 4
Sample drawn by Adding Kth unit to the randomly chosen number j+k, j+2k….
Step 3
Determine the first number randomly b/n 1st # and kth
Step 2
Determine Sampling interval K (k=Population Size/ Sample size or N/n)
Step 1
Number each of the cases in your sampling frame with a unique number
1.5.2 Systematic Random Sampling Procedures Cont.….
1 .5.2 Systematic Random Sampling Cont.…..
1. Sample easy to select
2. Simple to implement
3. Sample evenly spread over
entire reference population
4. Provides a better random
distribution than SRS
5. Can be started without a
complete listing frame
6. It reduces the field cost.
7. Inferential statistics may be
used.
8. Conclusions & generalizations is
possible
9. It is not costly design
10. Required minimal expertise
knowledge
Advantages of SyRS Advantages of SyRS Cont.…
1 .5.2 Systematic Random Sampling Cont.…..
1. Not fit for periodical sample
2. Difficult to assess precision of
estimate from one survey.
3. linear trend
4. This is not free from error
5. Knowledge of population is
essential
6. Information of each individual is
essential.
7. Only for optimal size of
population
8. Population distribution should be
natural degree of randomness
9. There is a greater risk of data
manipulation
Limitation of SyRS Limitation of SyRS Cont.…
Cluster Sampling:
AKA block sampling.
A Cluster sampling is a form of sampling divided the
population in to groups or clusters.
Cluster sampling usually geographic or organizational.
Cluster sampling is an exampling of two stage sampling.
The cluster are homogeneous units.
Sampling units are groups rather than individuals.
1.5.3 Cluster Sampling
Cluster Sampling:
A sample of such cluster is then selected.
In pure cluster sampling whole cluster is sampled.
In simple multi stage cluster randomly chosen .
Types Cluster Sampling Methods:
1. One-stage sampling.
All of the elements within selected clusters are included in the sample.
2. Two-stage sampling.
A subset of elements within selected clusters are randomly selected for inclusion in the sample
1.5.3 Cluster Sampling Cont.…
1.5.3 Cluster Sampling Procedures
Step 4
Sample of such clusters is then selected & all units from the selected clusters are studied..
Step 3
Population divided into clusters of homogeneous units & geographical contiguity
Step 2
A sample of respondents within those areas is selected.
Step 1
A sample of areas is chosen
1.5.3 Cluster Sampling Cont.…
1. Most economical/ Cheaper
2. Larger sample for a similar fixed
cost
3. Less time for listing &
implementation
4. Also suitable for survey of
institutions
5. Reduced cost of personal
interviews
6. It may be a good representative
of the population.
7. It is an easy method.
8. It is practicable & highly
applicable in education.
9. Observations can be used for
inferential purpose.
10. Feasible
11. Reduced variability
Advantages of Cluster S. Advantages of Cluster S.
1.5.3 Cluster Sampling Cont.…
1. Most economical/ Cheaper
2. Larger sample for a similar fixed
cost
3. Less time for listing &
implementation
4. Also suitable for survey of
institutions
5. Reduced cost of personal
interviews
6. It may be a good representative
of the population.
7. It is an easy method.
8. It is practicable & highly
applicable in education.
9. Observations can be used for
inferential purpose.
10. Feasible
11. Reduced variability
Advantages of Cluster S. Advantages of Cluster S.
1.5.3 Cluster Sampling Cont.…
1. Cluster sampling is not free from
errors.
2. It is not comprehensive.
3. Higher sampling error
4. Biased samples
5. May not reflect the diversity of
the community.
6. Other elements in the same
cluster may share similar
characteristics.
7. Provides less information per
observation than an SRS
Limitation of Cluster S.
Limitation of Cluster S.
Stratified Sampling:
A sampling method applied to extract a representative
sample from a heterogeneous population
Adequate representation of minority subgroups of interest
can be ensured by stratification & varying sampling fraction
between strata as required
Finally, since each stratum is treated as an independent
population, different sampling approaches can be applied to
different strata
1.5.4 Stratified Sampling
Post Stratification:
Stratification is sometimes introduced after the sampling
phase in a process called "post stratification“.
This approach is typically implemented due to :
Lack of prior knowledge of an appropriate stratifying
variable
when the experimenter lacks the necessary
information to create a stratifying variable during the
sampling phase.
1.5.4 Stratified Sampling Cont..
In SS Design:
1. Stratum variables are mutually exclusive (non-over lapping)
2. The population (elements) homogenous within-stratum
3. the population (elements) heterogeneous between the strata.
When we use SS:
A. Population groups may have different values for the responses of interest.
B. If we want to improve our estimation for each group separately.
C. To ensure adequate sample size for each group.
1.5.4 Stratified Sampling Cont..
1.5.4 Stratified Sampling Procedures
• The basis of common characteristic(s) of the items to be put in each stratum
• Strata are purposively formed and are usually based on past experience and personal judgment of the researcher.
Form of strata
• Simple random sampling • Systematic sampling can be used if it is considered
more appropriate in certain situations
Selection of items in each
stratum
• Proportional allocation • Optimum allocation (with equal cost) • Optimum allocation (with unequal cost)
Allocate of sample size of
each
stratum?
1.5.4 Sample Allocation for Stratified Sampling Design
• is more effective for comparing strata which have different error possibilities
• is less efficient for determining population characteristics.
Disproportionate
• It refers to the selection from each sampling unit of a sample that is proportionate to the size of the unit
• variables used as the basis of classifying categories and increased chances of being able to make comparisons between strata
Proportionate
• It refers to selecting units from each stratum • Each stratum should be in proportion to the
corresponding stratum the population.
Optimum allocation
1 .5.4 Stratified Sampling Design Cont.…..
It is a good representative of the population.
It is an improvement over the earlier technique of sampling.
It is an objective method of sampling.
Observations can be used for inferential purpose
Estimate could be made for each stratum
It have a smaller variance
Reduce survey costs.
1. It is difficult to decide the relevant
criterion for stratification.
2. Sampling frame is needed for each
stratum
3. There is a risk of generalization.
4. It is costly and time consuming
method
Advantages of SS Limitation of SS
1 .5.4 Stratification Vs. Clustering
BASIS FOR COMPARISON
STRATIFIED SAMPLING CLUSTER SAMPLING
Meaning
Population is divided into
homogeneous segments, and
then the sample is randomly
taken from the segments.
The members of the population are
selected at random, from naturally
occurring groups called 'cluster'.
Sample Randomly selected individuals
are taken from all the strata.
All the individuals are taken from
randomly selected clusters.
Selection Individually Collectively
Homogeneity Within group Between groups
Heterogeneity Between groups Within group
1 .5.4 Stratification vs. Cluster Cont.…
BASIS FOR COMPARISON
STRATIFIED SAMPLING CLUSTER SAMPLING
Cost It is costly and time
consuming method. Cheaper
Representative Sample more representative
Usually not representative of whole
population
Bifurcation Imposed by the researcher Naturally occurring groups
Objective To increase precision and
representation.
To reduce cost and improve efficiency.
1 .5.4 Stratification vs. Cluster Cont.…
Video Presentation\Multistage Sampling
final_setegn_presentation.mp4
1.5.5 Multistage Sampling
1.5.6 Summary of Presentation How We Select D/t Types of Sampling Method
1. C.R Kothari 1990, Research Methods & Techniques: Sampling Design, Second Edition, New Age International (P) Ltd., Publisher, New Delhi.55-66.
2. Dr. Prabhat Pandey and Dr. Meenu Mishra Pandey 2015, RESEARCH METHODOLOGY: TOOLS AND TECHNIQUES: Research Design: Published by Buzau, Al. Marghiloman 245 bis, 120082 , Romania.18-23.
3. GeoffreyM., David D and David F. 2005,Essential of Research Design and Methodology: Planning and Designing a Research Study, Published by John Wiley & Sons, Inc., Hoboken, New Jersey.26-65.
4. Mark Saunders,Philip Lewis and Adrian Thornhill 2009,Research Methods for Business Students: Selection Sample,Fifth edition, Published by Pearson Education Limited Edinburgh Gate Harlow, England.210-256.
5. U university of Bhojanna 2007, Research Methods for Management School of Distance Education Bharathiar University,Sampling Design, EXCEL BOOKS PRIVATE LIMITED A-45, Naraina, Phase-I,, New Delhi. 73-88.
6. Uma sekaran 2003, Research Methods for Business: Sampling, Fourth Edition, Published by John Wiley & Sons, Inc., Hoboken, New Jersey.263-276.
REFERENCE
THE END!!!