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[1] Introduction to Survey Sampling Frame and Survey Error, Notation,…
[1] Introduction to Survey Sampling Frame
and Survey Error
(1) How to collect data ?
Survey
Questionnair
Interview
Social listenning
(2) Census VS Sample Survey
1. Census
Obtain data from a
population
2. Survey
Gather information from a
sample
(3) Parameter VS Statistic
Numerical measure
1. Parameter
Measure calculated for a
population
2. Statistic
Measure calculated for a
sample
(4) What is a survey ?
Gathered mainly be asking people questions
Typically collected from a
sample
Collected by
1. Interview administered method
2. Self-administered method
(5) What do you need to know to design a survey ?
The target population
The sampling frame
The sample design
The mode of data collection
Ongoing survey or One-time survey
(6) Two approaches to survey sampling
1. Probabilitiy samples
A know probability of selection
Randomness
or
Chance
Example
Simple random sampling
Cluster sampling
Startified random sampling
Systematic sampling
2. Non-probability samples
Unknow probability of selection
Judgment
Example
1. Snowball samples
Start with one person to find other people
[Respondent driven sampling]
Homeless, HIV+
Problems
No prob. mechanism for inital selection
No guarantee that other characteristics will accurately reflect the population
2. Quota samples
Problems
No guarantee that other characteristics will accurately reflect the population
No prob. mechanism for inital selection
The number of people with certain characteristics meet predetermained quotas
Education, Race
3. Convenience samples
People who are the easiest to get participate
Volunteer, Research opportunity
Problems
No prob. mechanism for inital selection
Miss people with certain charateristics
(7) Target VS Frame population
1. Frame
Set of materials used to designate a sample of units
2. Target population
Set of households, people or businesses of interest for inference
(8) Mapping
Reality
[i.] Element in the target population that is not on the sampling frame
one-to-zero mapping
Problems
Solution
Supplemental frames
Zero chance of selection
[ii.] Sampling frame contains an element that does not exist in the target population
zero-to-one mapping
Problems
Solution
Screening is needed to dertermine this
Rejecting blank
Ineligible units, Foreign units, or Blanks
Smaller sample size
[iii.] Target population Elements appears more than one on sampling frame
one-to-many mapping
Problems
Solution
Remove from list before selection
Unequal probability of selection weights
Duplicates: Non-EPSEM
[iv.] More than one target population elements represented by one sampling frame element
many-to-one mapping
Problems
Solution
Take all elements within selected clusters
Clustering
[v.] Many to many matching
many-to-many mapping
Problems
Solution
Weigting + Subsampling
More than one population element can be selected by more than one frame element
Ideal
[0.] Perfect mapping
one-to-one mapping
(9) Survey Error
Error
1. Bias
Systematic error
Error that tend to agree
2. Variance
Variable error
Error that tend to disagree
MSE = (bias)^2 + variance
(10) Types of Error in Survey
1. Coverage error
Happens when
sampling frame does not match the target population
{Coverage bias}
Ineligible unit
Noncoverage unit
SPF not contain all of the members of target population
SPF contain individuals who do not belong to the target population
[Overcoverage]
2. Sampling error
Occurs due to
selective sample
instead of the entire population
Sampling bias
Sampling variance
3. Nonresponse error
Occurs when an estimate calculated using only
respondents differs
from that calculated using the entire sample data
{Nonresponse bias}
Unit nonresponse
Occurs when the sample member
does not provide any information
1.Noncontact
2.Refusal
3.Inability to participate
Item nonresponse
Occurs when a respondent
fails to answer a survey question
Example
2 more items...
4. Measurement error
Occurs when the answer from the survey respondent
does not match the true answer
to the survey question
Respondent
Interviewer
Questionnair
Mode of data collection
1 more item...
Ambiguous or confusing questions
Record responses incorrectly or unintentionally affect answers
Either deliberately or unintentionally provide incorrect information
Notation
N
Number or elements in your
population
n
Number of elements in your
sample
Y
Population value
for survey variable of interest
y
Sample value
for survey variable of interest
i
Counter for units in the sample or population
Adjust the sampling rate
m = n(1-pb)
pb
estimated proportion of blank frame elemants
n
desired final sample size of population elements
m
the number of frame elements to select
Terminology
1. Target population
ประชากรเป้าหมาย
Space + Time
Set of things of interest
2. Sampling frame
กรอบตัวอย่าง
List and procedure used to identify an element in the target population
3. Sample or element
หน่วยตัวอย่าง
Fundamental unit in the population
Different unit ex. person or household
EPSEM
Euqal Probability Selection Method
f = n/N
Weighting IIllustration
1. Unweighted mean
2. Weighted mean
Non-EPSEM
d(i)
Number of duplicates for a given selected element
1/d(i)
Weight observation for that selection with probability
Note
1. Socially desirable question
Overreport (+)
2. Socially undesirable question
Underreport (-)
Sampling Fraction
f = n/N
[2] Simple Random Sampling
and Systematic Sampling