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1 / INTRODUCTION TO
BASIC CONCEPTS IN
EXPERIMENTAL DESIGN

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INTRODUCTION

The term experimental design refers to five interrelated activities
reguired in the investigation of scientific or research hypotheses. These
activities, listed in the order performed, are as follows:

1. Formulate statistical hypotheses and make plans for the collection and
analysis of data to test the hypotheses. A statistical hypothesis is a state-
ment about one or more parameters of a population. Statistical hypoth-
eses are rarely identical to research or scientific hypotheses butare
testable formulations of research hypotheses. Em

- State decision rules to be followed in testing the statistical hypotheses.
. Collect data according to plan.
. Analyze data according to plan.

. Make decisions concerning the statistical hypotheses based on decision
rules and inductive inferences concerning the probable truth or falsity
of the research hypotheses.

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The term experimental desigri is also used in a more restricted sense to
designate a particular type of plan for assigning subjects to experimental
conditions and the statistical analysis associated with the plan. The mean-
ing of the term is generally clear from the context in which it is used.

SUBJECT MATTER AND GENERAL
ORGANIZATION OF THIS BOOK

The concepts and procedures involved in carrying out steps l, 2,
4, and 5 above comprise the subject matter of this book. Experimental design
is only one of the many facets of scientific research. A carefully conceived
and executed design is of no avail if the scientific hypothesis that originally
led to the experiment is without merit.

A detailed examination of the logical and statistical aspects of
specific experimental designs begins in Chapter 4. The first three chapters
provide an overview of experimental designs. a review of basic statistical

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