Biostatistics

7.1 INTRODUCTION 215
7.1 INTRODUCTION
One type of statistical inference, estimation, is discussed in the preceding chapter. The
other type, hypothesis testing, is the subject of this chapter. As is true with estimation,
the purpose of hypothesis testing is to aid the clinician, researcher, or administrator in
reaching a conclusion concerning a population by examining a sample from that
population. Estimation and hypothesis testing are not as different as they are made to
appear by the fact that most textbooks devote a separate chapter to each. As we will explain
later, one may use confidence intervals to arrive at the same conclusions that are reached by
using the hypothesis testing procedures discussed in this chapter.
Basic Concepts In this section some of the basic concepts essential to an understanding
of hypothesis testing are presented. The specific details of particular tests will be
given in succeeding sections.
DEFINITION
A hypothesis may be defined simply as a statement about one or more
populations.
The hypothesis is frequently concerned with the parameters of the populations
about which the statement is made. A hospital administrator may hypothesize that the
average length of stay of patients admitted to the hospital is 5 days; a public health nurse
may hypothesize that a particular educational program will result in improved communication
between nurse and patient; a physician may hypothesize that a certain drug
will be effective in 90 percent of the cases for which it is used. By means of hypothesis
testing one determines whether or not such statements are compatible with the available
data.
Types of Hypotheses Researchers are concerned with two types of hypotheses—
research hypotheses and statistical hypotheses.
DEFINITION
The research hypothesis is the conjecture or supposition that motivates
the research.
It may be the result of years of observation on the part of the researcher. A public
health nurse, for example, may have noted that certain clients responded more readily to a
particular type of health education program. A physician may recall numerous instances in
which certain combinations of therapeutic measures were more effective than any one of
them alone. Research projects often result from the desire of such health practitioners to
determine whether or not their theories or suspicions can be supported when subjected to
the rigors of scientific investigation.