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Summarised Overview

Sample size refers to the number of individuals or observations included in a study
or experiment. The determination of an appropriate sample size is crucial for obtaining
accurate and reliable results. Several factors influence the selection of the sample size,
including the desired level of precision, the variability of the population, the research
design, the available resources, and the statistical methods to be used.

The optimum sample size is the one that gives us the right balance between accuracy
and practicality which is determined using statistical formulas or power calculations
that take into account factors such as the desired level of significance, effect size, and
statistical power. Errors in sampling can happen when the sample doesn’t represent the
whole group, when there’s natural variation, or when some people refuse to participate.
Determining an appropriate sample size is crucial for obtaining reliable results. Careful
consideration of these factors is necessary to ensure the validity and generalisability of
the study outcomes.

Assignments

1. Calculate sample size based on Cochran’s formula: N=20000, p=0.5, level of pre-
cision is 5 percent, at 95 percent level of confidence.

2. You are conducting a study to investigate the opinions of residents in a city regard-
ing a proposed development project. The population size of the city is 30000. You
want to determine the sample size needed for your study with a 95 percent confi-
dence level and a margin of error of 0.05. The population proportion is estimated to
be 50 percent. Calculate the sample size required.
3. A study is conducted to analyse the voting preferences of registered voters in a
district. The population size of registered voters is 50000. The level of confidence
is 99 percent and margin of error is 0.03. The population proportion is estimated to
be 0.4. Calculate the sample size required.

4. Differentiate sampling errors and non-sampling errors.
5. Explain how an optimum sample size can be estimated and its relevance.

6. What factors influence the sample size and how?
7. Does the variability of the data affect the sample size? If yes, explain how it affects
the sample size.

78 SGOU - SLM -MCom Research Methodology