Unit 2: Data Collection

Question 1

Classification of statistical data

Answer 1

1. Primary vs. Secondary
2. External vs. Internal

Question 2

data measured by the researcher / agency that published it.

Answer 2

primary data

Question 3

any republication of data by another agency.

Answer 3

secondary data

Question 4

information that relates to the operations and functions of the organization collecting the data.

Answer 4

internal data

Question 5

information that relates to some activity outside the organization collecting the data.

Answer 5

external data

Question 6

General classification of collecting data

Answer 6

Census and sample survey

Question 7

a.k.a. complete enumeration
- is the method of gathering the information of interest or pertinent data from every unit in the population.

Answer 7

census

Question 8

method of gathering data from a small but representative cross section of the population.

Answer 8

sample survey

Question 9

advantages of sample survey

Answer 9

Speed and timeliness
- data on the population can be gathered faster ensuring uniformity.

Economy
- information gathering and data analysis is cheaper.

Quality and accuracy
- when properly conducted, a sample survey usually yields more accurate results since a small highly skilled group of workers is likely to make fewer errors in the collection and handling of data than a large census force would.

Feasibility
- some data gathering methods require the destruction of a unit to obtain the required information, e.g., lifetime of a bulb.

Question 10

Methods of collecting statistical data

Answer 10

Survey method
Observation method
Experimental method
Use of existing studies
Registration method

Question 11

questions are asked to obtain information.

Answer 11

survey method

Question 12

ways to administer survey

Answer 12

telephone interview
mailed questionnaire
online survey
personal in-home survey
personal mall intercept survey

Question 13

makes possible the recording of behavior but only at the time of occurrence

Answer 13

observation method

Question 14

• a method designed for collecting data under controlled conditions.
• is an operation where there is actual human interference
  with the conditions that can affect the variable under study.

Answer 14

experiments

Question 15

e.g., census, health statistics, and weather bureau reports.

Documentary sources - published or written reports, periodicals, unpublished documents, etc.

Field sources – researchers who have done studies on the area of interest are asked personally or directly for information needed

Answer 15

use of existing studies

Question 16

e.g., car registration, student registration, and hospital
admission.

Answer 16

registration method

Question 17

Sampling methods

Answer 17

• non-probability
• probability

Question 18

• not all members of the population have a chance to participate in the study
• often used in exploratory and qualitative research.

Answer 18

non-probability sampling

Question 19

• every element of the population a (known) nonzero chance of being selected in the sample
• often used in quantitative research

Answer 19

probability sampling

Question 20

population from which information is desired.

Answer 20

target population

Question 21

collection of elements from which the sample is taken.

Answer 21

sampled population

Question 22

listing of all the individual units in the population.

Answer 22

population frame

Question 23

sets out to make a sample agree with the profile of the population based on some pre-selected characteristics

Answer 23

purposive sampling

Question 24

selects a specified number of sampling units possessing certain characteristics.

Answer 24

quota sampling

Question 25

selects sampling units that come to hand or are convenient to get information from.

Answer 25

convenience sampling

Question 26

selects sample in accordance with an expert’s judgment.

Answer 26

judgment sampling

Question 27

a sampling method which existing subjects provide referrals to recruit samples required for a research study.

Answer 27

snowball sampling

Question 28

commonly used probability sampling methods are:

Answer 28

1. Simple random sampling
2. Stratified random sampling
3. Systematic sampling
4. Cluster sampling
5. Multistage sampling

Question 29

method of selecting n units out of the N units in the population in such a way that every distinct sample of size n has an equal chance of being drawn. The process of selecting the sample must give an equal chance of selection to any one of the remaining elements in the population at any one of the n draws.

Answer 29

Simple Random Sampling

Question 30

Explain the process of simple random sampling

Answer 30

Step 1: Make a list of the sampling units and number them from 1 to N.

Step 2: Select n numbers from 1 to N using some random process, for example, the table of random numbers. n is distinct for SRSWOR, not necessarily distinct for SRSWR.

Step 3: The sample consists of the units corresponding to the selected random numbers.

Question 31

method of selecting a sample by taking every kth unit from an ordered population, the first unit being selected at random.

Here k is called the sampling interval; the reciprocal 1/k is the sampling fraction.

Answer 31

1-in-k Systematic sampling

Question 32

Explain the linear process of systematic sampling

Answer 32

Method A
Step 1: Number the units of the population consecutively from 1 to N.

Step 2: Determine k, the sampling interval using the formula k = N/n.

Step 3: Select the random start r, where 1 ≤ r ≤ k. The unit corresponding to r is the first unit of the sample.

Step 4: The other units of the sample correspond to r + k, r + 2k, r + 3k, and so on.

Question 33

Explain the circular process of systematic sampling

Answer 33

Method B
Step 1: Number the units of the population consecutively from 1 to N.

Step 2: Let k be the nearest integer less than N/n.

Step 3: Select the random start r, where 1 ≤ 𝑟 ≤ 𝑁. The unit corresponding to r is the first unit of the sample.

Step 4: Consider the list of units of the population as a circular list, i.e., the last unit in the list is followed by the first. The other units in the sample are the units corresponding to r + k, r + 2k, r + 3k,…, r+ (n-1)k.

Question 34

the population of N units is first divided into subpopulations called strata. Then a simple random sample is drawn from each stratum, the selection being made independently in different strata.

Answer 34

Stratified random sampling

Question 35

Explain the process of stratified random sampling

Answer 35

Step 1: Divide the population into strata. Ideally, each stratum must consist of more or less homogeneous units.

Step 2: After the population has been stratified, a simple random sample is selected from each stratum.

Question 36

A common strategy is to select a number of units from each stratum that is proportional to the number of sample units (or size) within each stratum

Answer 36

proportional allocation

Question 37

method of sampling where a sample of distinct groups, or clusters, of elements is selected and then a census of every element in the selected clusters is taken.

Answer 37

Cluster sampling

Question 38

Explain the process of cluster sampling

Answer 38

Step 1: Number the clusters from 1 to N.

Step 2: Select n numbers from 1 to N at random. The clusters corresponding to the selected numbers form the sample of clusters.

Step 3: Observe all the elements in the sample of clusters.

Question 39

• the population is divided into a hierarchy of sampling units corresponding to the different sampling stages. In the first stage of sampling, the population is divided into primary stage units (PSU) then a sample of PSUs is drawn.
• In the second stage of sampling, each selected PSU is subdivided into second-stage units (SSU) then a sample of SSUs is drawn.

Answer 39

Multistage sampling