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Types of Sampling Presenation

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SAMPLING

Types of Probability Sampling

• Simple Random Sampling


• Systematic Sampling with a Random Start
• Stratified Random Sampling
• Cluster Sampling
• Multistage Sampling
Simple Random Sampling

• Gives equal chances to all sampling units to be included as a


sample
1. drawing of lots or use of table of random digits
Systematic Sampling with a Random Start

• Selecting sample from a population by taking the kth units from an


ordered population, from the first unit which is selected at random.
• K is called the sampling interval= total population divided by sample
size
• Ordered list of population elements is required
Stratified Random Sampling

• Selecting a random sample from subgroups or strata into which a population has been subdivided
using either simple random or systematic sampling

• Requires grouping of the population into less homogenous subgroups or strata before sampling is
drawn

• Sample per group is drawn using=population (sub group)/total


population*desired sample size
Cluster Sampling

• Selecting a sample of groups or cluster of elements


• Usually exclusive sub-populations, which together comprise a population
• Usually heterogeneous sections, where each section is considered a cluster
• Size of the population of clusters=the number of clusters in the population
• Cluster size=number of elements in a cluster
A study on Attitudes Towards Cheating of College Freshmen In a
Cluster Private School . 100 students as respondents and 50 is the desired
sample size. Students ,may be divided into 10 heterogeneous
Sampling: groups

Population: All the 10 classes/clusters


Frame: List of 10 clusters/groups
Sampling Unit: One group/cluster with 10 members
Steps:
1. Number the 10 groups from 1 to 10
2. Using simple random or systematic sampling with random, draw 5
numbers. Example, 2 6 7 9 1 are chosen
3. Identify the groups represented by the numbers drawn
4. Study all the students in the five sample classes/groups drawn
Multistage Sampling

• Selection of sample is accomplished in two or more stages


• Used when population can be divided into hierarchies
In a Study of Men’s Participation in Child Care where a sample of
Multistage 135 married men with 0-6 years old children from a certain
province. You select 3 of the 7 towns of the province and 3
Sampling barangays in each sample town and 15 married men in each
barangay

Population: All the men with 0-6 years old children in the province
Sampling Frame: List of men with 0-6 years old children
Sampling Unit: A man with 0-6 years old children
Steps:
1. Draw 3 sample towns in the province using simple random or systematic sampling
2. Draw a sample of 3 barangays in each of the 3 sample towns using simple random
or systematic sampling
3. Draw a sample of married men with 0-6 years old children in each of the 3 sample
barangays in each of the 3 sample towns using simple random or systematic
sampling
Determination of Sample Size

• CONSIDERATIONS:
1. availability of resources
2. the requirements of a proposed plan of analysis
How Sample Size is Computed?

• If Population is more than 10,000


Z2pq
n = ---------------
d2
Where:
n = the desired sample size
Z = the standard normal deviate, usually set at 1.96, corresponds to the 95% level
of confidence
p = proportion in the target population, if none then use 50 %
q = 1.0-p
d = degree of accuracy desired, usually set at either 0.05,0.2, or 0.01
How Sample Size is Computed? (Parel, et.al., 1985)

• The Total Population N is considered


NZ2 (p (1-p))
n = ------------------------------
Nd2 + Z2 (p (1-p))
Where:
N = Population
n = the desired sample size
Z = the standard normal deviate, set at 1.96, corresponds to the 95% level of
confidence
p = proportion in the target population, if none then use 50 %
d = degree of accuracy desired, usually set at either 0.05, 0.25, or 0.01
How Sample Size is Computed?

• Slovin’s Formula
N
n = ------------------
( 1 + N) (05)2
Where:
N = Population
n = the desired sample size

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