Educational Survey Research

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Quantitative research methods in educational planning
Series editor: Kenneth N.Ross

Module
Kenneth N. Ross

Sample design for educational survey research

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UNESCO International Institute for Educational Planning

Module 3

Sample design for educational survey research

Content
1. Basic concepts of sample design for educational survey research Populations : desired, defined, and excluded Sampling frames Representativeness Probability samples and non-probability samples Types of non-probability samples 1. Judgement sampling 2. Convenience sampling 3. Quota sampling

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Types of probability samples
1. Simple random sampling 2. Stratified sampling 3. Cluster sampling 1. Mean square error

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The accuracy of estimates obtained from probability samples 13 2. The accuracy of individual sample estimates 3. Comparison of the accuracy of probability samples

Sample design for two-stage cluster samples
1. The design effect for two-stage cluster samples 2. The effective sample size for two-stage cluster samples

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Sample design tables for two-stage cluster samples

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© UNESCO

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Module 3

Sample design for educational survey research

2. How to draw a national sample of students: a hypothetical example for ‘country x’ 3. How to draw a national sample of schools and students: a real example for Zimbabwe 4. The estimation of sampling errors The Jackknife Procedure

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5. References Appendix 1
Random number tables for selecting a simple random sample of twenty students from groups of students of size 21 to 100

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Appendix 2 Appendix 3

Sample design tables (for roh values of 0.1 to 0.9)

Estimation of the coefficient of intraclass correlation

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http://www.sacmeq.org and http://www.unesco.org/iiep

Basic concepts of sample design for educational survey research Sampling in educational research is generally conducted in order to permit the detailed study of part, rather than the whole, of a population. The information derived from the resulting sample is customarily employed to develop useful generalizations about the population. These generalizations may be in the form of estimates of one or more characteristics associated with the population, or they may be concerned with estimates of the strength of relationships between characteristics within the population. Provided that scientific sampling procedures are used, the selection of a sample often provides many advantages compared with a complete coverage of the population. For example, reduced costs associated with gathering and analyzing the data, reduced requirements for trained personnel to conduct the fieldwork, improved speed in most aspects of data summarization and reporting, and greater accuracy due to the possibility of more intense supervision of fieldwork and data preparation operations. The social science research situations in which sampling is used may be divided into the following three broad categories: experiments – in which the introduction of treatment variables occurs according to a pre-arranged experimental design and all extraneous variables are either controlled or randomized; surveys – in which all members of a defined target population have a known

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© UNESCO

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Module 3

Sample design for educational survey research

non-zero probability of selection into the sample; and investigations – in which data are collected without either the randomization of experiments or the probability sampling of surveys. Experiments are strong with respect to internal validity because they are concerned with the question of whether a true measure of the effect of a treatment variable has been obtained for the subjects in the experiment. Surveys, on the other hand, are strong with respect to external validity because they are concerned with the question of whether the findings obtained for the subjects in the survey may be...
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