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But, how do we do so if there exists variability from one sample to the next This chapter will
address this question
7.1 The Concept Behind Hypothesis Testing
So, you have a research question… what now The question might at first seem obvious: let‟s
run a study. This question, however, needs some special treatment before anything else happens,
especially if the study comes at a significant cost.
For instance, suppose we‟re interested in determining whether pesticides damage the soil in
which we grow the majority of our food. This is a loaded curiosity. We first need to fully define
how it is that we would conduct such a study. For instance, will be comparing two regions, one
that has been sprayed with pesticides and one that hasn‟t been sprayed What is it, exactly, that
we will measure in order determine the level of soil damage
First and foremost, we need to formulate a hypothesis, or a belief about what it is that we expect
to see. For example,
Our hypothesis is that pesticides inflict serious damage on sprayed soils
Great, so we know what we believe. Did we just state what we wanted to happen Probably not.
We‟ll usually formulate a hypothesis based on some existing observations. Perhaps we‟re seeing
that plants aren‟t producing as many edibles as previously thought. Or, maybe we‟re finding
rising levels of cancers. (By the way, all of the above are becoming eminent public concerns in
the U.S. and beyond.) So, based on these observations, we‟re forming an educated belief on the
effect of pesticides.
The next critical question:
How will we measure “soil damage”
This can be a controversial question and may lack a consensus of an answer. Will it be measured
by the quantities of beneficial microbes present in the soil By the soil‟s pH level By the
amount of nitrogen it contains
However we choose to measure “soil damage,” we want to be sure that we are being accurate.
That is, we need to be sure that we are actually measuring what we say we‟re measuring. This
sounds infantile, but it happens all the time that researchers say they‟re measuring something that
they‟re not actually measuring.
So, suppose we do some research and conclude that we test for soil damage by determining the
weight of vegetables harvested from these plants and comparing the average weight per plant for
the experimental group (some determined quantity of pesticides sprayed). We find that healthy
plants produce about 30 lbs. of some vegetable across their seasonal life span. Will the average
plant yield for plants sprayed with pesticides be lower
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