sampling process and collection of data[1]
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MODULE 3MODULE 3
STATISTICAL TOOLS IN RESEARCHSTATISTICAL TOOLS IN RESEARCH
Sampling ProcessSampling Process
Collection of dataCollection of data
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THE SAMPLING PROCESSTHE SAMPLING PROCESS
The Concept of Sampling
Sampling is defined as the process of selecting a
few from a bigger group to become the basis for
estimating or predicting a fact, situation oroutcome regarding the bigger group.
Sampling is also defined as the process of
selecting suitable or representative samples used
for the purpose of determining the characteristics
or properties of the whole population (Webster,
1986)
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SAMPLESAMPLE
defined as any aggregate drawn from a population
(Ferguson, 1976)
It is a small group that is observed while the
population is the larger group about which thegeneralization is made.
It must be adequate in size in order to produce
reliable results.
It should validly represent the whole population
involved in the study.
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POPULATIONPOPULATION
It is the group to which the results will be
generalizable.
It consists of attributed qualities and behavior of a
people or inanimate objects or opinions of peoplecomposing a nation. (Sanchez, 1997)
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STEPS USED IN SAMPLINGSTEPS USED IN SAMPLING
identification of the population
determination of the required sample size
election of the sample
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SAMPLING TECHNIQUESSAMPLING TECHNIQUES
Types of Sampling Techniques
The Probability Sampling - the ratio of the
number of outcomes produced in a given
population taken from the total population(Webster, 1986).
The Non-Probability Sampling - uses no system
of selecting samples and therefore, there is no
guarantee of equal chances of representation in
the samples. Hence, the samples taken may not be
the representative samples of the population
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A. THE PROBABILITY SAMPLINGA. THE PROBABILITY SAMPLING
Classification of Probability Sampling Random Sampling is the drawing of samples of the study which gives
each participant equal chance of being selected. To do randomsampling it is necessary to define the population, list all members ofthe population and then select the sample by employing adequate
procedure. Systematic sampling is the technique of choosing the samples from
the population after determining the sample size of the study whereeach class is treated as a different population. It is done by listing thenames of the identified samples following a logical, systematic oralphabetical or whatever acceptable arrangement.
Cluster sampling involves the selection of samples involving a clusteror a group and it is usually applied on a geographical basis in aheterogeneous population. This sampling is sometimes called areasampling because it is frequently applied on a geographical basis.
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CLASSIFICATION OF THE NONCLASSIFICATION OF THE NON--
PROBABILITY SAMPLINGPROBABILITY SAMPLING
Convenience or accidental sampling - involvesthe selection of the samples based on theconvenience of the researcher
Purposive or deliberate sampling - samples areselected based on the decision or judgment of theresearcher on who best qualifies to answer theobjectives of the study
Quota sampling - identifies quota or number ofsamples to be involved in the study with thequalities proportionate to the population of thestudy
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WAYS TO DETERMINE THE SAMPLE SIZEWAYS TO DETERMINE THE SAMPLE SIZE1. Use of formula:
n= N where n = size of the sample
1+(N)(e)2 1 = constant N = size of population
e = desired margin of error
example: Determine the sample size if the total population of the study is 5000 using a 5% marginor error.
n = 5000
1+5000 (0.5)
n = 5000
1+5000(.0025)n = 5000
1+12.5
n = 500013.5
n = 370 The sample size is 370 respondents
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2.2. USE OF PERCENTAGEUSE OF PERCENTAGE
Gay (1976) give some minimum sizes
Descriptive research 10% of a large population of
1,000 or more; 20% for a small number of population of
500 and less. Correlational research 30 subjects
Experimental research 15 subjects per group of 30 per
group as preferred by some authorities
Ex post facto or causal comparative 15 subjects pergroup
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USE OF SPECIFIC MARGIN OF ERRORUSE OF SPECIFIC MARGIN OF ERRORPopulation Margin of Error / Sample
Representative
+1% +2% +3% +4% +5% +10%
500 NA NA NA NA 222 83
1,500 NA NA 638 441 316 94
2,500 NA 1,250 769 500 345 96
3,000 NA 1,364 811 517 353 97
4,000 NA 1,538 870 541 364 98
5,000 NA 1,667 909 556 370 98
6,000 NA 1,765 938 566 375 98
7,000 NA 1,842 956 574 378 99
8,000 NA 1,908 976 580 381 99
9,000 NA 1,908 989 584 383 99
10,000 5,000 2,000 1,020 588 388 99
50,000 8,333 2,333 1,807 617 387 100
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COLLECTION OF DATACOLLECTION OF DATA
Data are the things we think with. They are the
raw materials of reflection, until by comparison,
combination and evaluation they are stepped up to
higher levels of generalization, where again theyserve as basic materials for higher thinking.
(Whitney, 1950).
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Structured self reporttechniques utilize a formal
written document which is usually referred to as
instrument.
interview schedule - when answered orally questionnaire - when answered using a paper and
pencil
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CLASSIFICATION OF DATACLASSIFICATION OF DATA
objective or subjective
quantitative or qualitative
attributes or variables
methods and types of research that the researcher
may use, e.g. historical, experimental, descriptive,
sociological and so on
primary or secondary raw or derived.
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SOURCES OF DATASOURCES OF DATA
Manuscripts
Relics
Fossils
Books Pamphlets
Magazines
Newspapers
Monuments and all kinds of specimen within human reach and
interpretation.
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CLASSIFICATION OF SOURCES OF DATACLASSIFICATION OF SOURCES OF DATA
(BEST, 1981)(BEST, 1981)
primary sources - official records of legislative
bodies, departments, school officials, minutes of
board meetings, annual bulletins course study,
curriculum guides, report cards and the like secondary sources - reports of a person on the
testimony of an actual witness of participant in an
event, history textbooks, encyclopedias and other
similar second hand account
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TOOLS OR TECHNIQUES USED IN THETOOLS OR TECHNIQUES USED IN THE
COLLECTION OF DATACOLLECTION OF DATA
A. Observation - considered as one of the oldest forms of
studying behavior
B. The Interview - a data-gathering device which enables
the researcher to draw information from the subject or
interviewee verbally in a face-to-face relationship.
C. Inquiry Forms
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TYPES OF OBSERVATIONTYPES OF OBSERVATION
Naturalistic observation - means watching and
describing behavior as it occurs in its natural
setting.
Participant observation - the person doing theresearch becomes actively involved in the lives of
the people being observed, thus, participant
observation is obtrusive.
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CHARACTERISTICS OF GOOD OBSERVATIONCHARACTERISTICS OF GOOD OBSERVATION
Observation should be carefully planned, systematic, and
perceptive
Observers should note the important details
Observers should be objective
Observers should separate the facts from the interpretation of
the facts
Observers should check and verify their observations with those
of other competent observers.
Observers should use appropriate instruments to systematize,quantify, and carefully record the results of their observations.
Observers should ensure that their observations are valid and
reliable.
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TYPE OF INTERVIEW ACCORDING TOTYPE OF INTERVIEW ACCORDING TO
STYLESTYLE
Formal Interview - utilizes an interview schedule
which consists of standard set of questions.
Answer sheet is also provided where answers to
specific questions may be written. Informal Interview - the interviewer is guided by
the interview guide which provides some salient
points on which the interview is focused
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IMPORTANT POINTS TO BE CONSIDERED INIMPORTANT POINTS TO BE CONSIDERED IN
THE CONDUCT OF INTERVIEWTHE CONDUCT OF INTERVIEW
Preparation- involves the preparation of an interview
guide, interview schedule and identification of possible
strategy to be used in the conduct of interview
Know the appropriate place and time for interview.
Select an ideal, comfortable place free from noise and
distraction and time, where, and when to conduct the
interview.
Develop rapport. The interviewer should develop
harmonious, friendly and cordial atmosphere with theinterviewee.
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Sustaining the interview - the interview should learn to
carry on the conversation smoothly until the end of the
interview by using some key words that will help sustain
the interview
Interview Recording - a portable tape recorder could be
used to accurately document the interview but permission
to use one should be requested from the interviewee.
Clarification of the statements is made by the interviewee.
closing the Interview. The interviewer should end theinterview with the expression of deep gratitude and
appreciation for the time, effort and generosity of the
interviewee in providing information relevant to the study.
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Inquiry Forms
Questionnaire - defined by Good (1954) as a list
of planned, written questions related to a
particular topic, with space provider for indicating
the response may be sent by mail to individualswho are called respondents but it can also be
administered personally to groups of individuals
The Opinionnaire - or attitude scale measures
the attitude or belief of an individual.
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TYPES OF QUESTIONNAIRETYPES OF QUESTIONNAIRE
Structured - structured questionnaire asks a
question and provides several possible answers
Unstructured - primarily asks questions, but no
suggested answers are given by the investigator.According to Nutt et. al (1966)it provides more
freedom to the respondents but are difficult to
analyze when large groups of subjects are used.
The decision as to which type of questionnaire
to use is based on the problem being studied and
other practical factors.
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PRINCIPLES IN CONSTRUCTING APRINCIPLES IN CONSTRUCTING A
QUESTIONNAIREQUESTIONNAIRE
Define or qualify terms that could easily be misinterpreted.
Be careful in using descriptive adjectives and adverbs that have
no agreed-upon meaning.
Be careful of inadequate alternatives
Avoid double negatives.
Avoid the double-barreled question
Underline a word if you wish to indicate special emphasis
Avoid unwarranted assumptions.
Phrase questions so that they are appropriate for allrespondents.
Design questions that will give a complete answer.
Provide for the systematic quantification of responses.
Consider the possibility of classifying the responses.
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CHARACTERISTICS OF A GOODCHARACTERISTICS OF A GOOD
QUESTIONNAIREQUESTIONNAIRE
It deals with a significant topic, on which the respondent will
recognize as important enough to warrant spending his time on.
It seeks only information which cannot be obtained from other
sources such as school reports or census data.
It is as short as possible only long enough to get the essentialdata.
It is attractive in appearance, neatly arranged, and clearly
duplicated or printed.
Directions are clear and complete, important terms are defined,each question deals with a single idea, all questions are worded
as simply and as clearly as possible, and the categories provide
an opportunity for easy, accurate and unambiguous responses.
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The questions are objective, with no leading suggestions as to
the responses desired.
Questions are presented in good psychological order, proceeding
from general to more specific responses. If possible,
embarrassing questions should be avoided. The responses are easy to tabulate and interpret.
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TYPES OF QUESTIONS IN PREPARATION OFTYPES OF QUESTIONS IN PREPARATION OF
THE QUESTIONNAIRETHE QUESTIONNAIRE
Open-ended Question or Free response questions. This
type will freely allows the respondents to express
themselves on the issue or the problem raised regarding
the study. The questions frequently asked are what, why
and how.
Closed Type or structural form of Questionnaire. It is
also called fixed alternative questions. It provides a list of
choices among enumerated alternatives as answers to the
specific question raised in the study.
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CRITERIA IN PREPARATION OF THECRITERIA IN PREPARATION OF THE
QUESTIONNAIREQUESTIONNAIRE
Knowing the two types of questions.
Utilize the knowledge and information you will gather from
the review of related literature.
Talk with persons who are knowledgeable on the
construction of the questionnaire can also help in the
preparation of the questionnaire such as your professors,
department heads or the deans of your college or university
officials.
Make the draft of your questionnaire and then submit it toyour advisers and other professors for comments and
suggestions.
Test the validity and reliability of your questionnaire using
dry-run.
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GUIDE IN ADMINISTERING THEGUIDE IN ADMINISTERING THE
QUESTIONNAIREQUESTIONNAIRE
Choose respondents carefully.
Secure the approval of the appropriate authorities
If the desired information is delicate or intimate in
nature, consider the possibility of providing foranonymous responses.
Try to get the aid of sponsorship.
Include a courteous and carefully constructedcover letter to explain the purpose of the study
Make a vigorous follow-up to increase the number
of returns.
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QUALITIES OF A GOOD INSTRUMENTQUALITIES OF A GOOD INSTRUMENT
Validity - measures what it claims to measure
Reliability - measures consistently, from one time to
another whatever it should measure
Sensitivity - the ability of an instrument to makediscriminations required for the resource problem
Objectivity - the degree to which the measure is
independent of personal opinions, subjective
judgment, biases and beliefs of the individual test user Feasibility - concerns the skills, cost and time needed
in preparing the test
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TYPES OF VALIDITYTYPES OF VALIDITY
1. Content validity shows how adequately the test
samples the universe of knowledge, attitudes, and skills
that a student is expected to master.
2. Construct validity is the degree to which scores on a
test can be accounted for by the explanatory constructs
of a sound theory.
3. Criterion-related validity is a broad terms that refers
to two different criteria.
a. predictive validity - which refers to the usefulness of a test in
predicting some future performance.
b. concurrent validity - which refers to the usefulness of a test
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