Page 61 - Exhibit No. 3 Copies of Instructional Materials Actually Used

Two factors may influence the degree of certainty about the inferences drawn
from a sample:

1. Findings based upon larger samples have more certainty than those based
on smaller ones. As a rule, "the larger the sample size, the more accurate
the findings.
2. The greater the variation in the study population with respect to the
characteristics under study for a given sample size, the greater the
uncertainty.

Bias must be avoided in the selection of the sample in order to achieve maximum
precision in estimates within a given sample size.

Examples of bias in the selection of a sample:

1. When sampling is done by a non-random method such as if the selection
is consciously or unconsciously influenced by human choice;
2. When the sampling frame (list, index or other population records) which
serves as the basis of selection, does not cover the sampling population
accurately and completely.
3. When a section of a sampling population is impossible to find or refuses
to cooperate.

Types of Sampling

There are three major types of sampling designs.

A. Probability Sampling

1. Random/Probability Sampling Design

This is a sampling design wherein each element in the population has
an equal au independent chance of selection in the sample. The concept of
independence means that the choice or one element is not dependent upon
the choice of another element the sampling or the selection or rejection of
the element does not affect the inclusion exclusion of another. For example,
if one of five close friends in a class was chosen but refuses to participate in
the survey if the other four are not chosen, and the researcher therefore is
forced to select either the five or none, then that sample will not be considered
as independent sample since the selection of one is dependent upon the
selection or the others.

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Nursing Research I