More on
Constructing Knowledge within the Scientific
Method
The following is a more
detailed discussion of key
components of the scientific method that will be emphasized in the
Biology
101/102 lab course. Please read
carefully and often to help you succeed in science and earn top marks
in the
introductory biology lab course.
A Generalized Outline
of the Scientific Method
1. Define the
question
2. Gather
information (less structured observations and literature research)
3. Form hypothesis
(see below)
4. Perform
experiment and collect data (structured and controlled observations)
5. Analyze data
(summarize, simplify and synthesize)
6. Interpret data
and draw conclusions that serve as a starting point for new hypothesis
7. Communicate
results (see Key
Elements of Scientific Reporting)
8. Retest
(frequently done by other scientists)
Fundamental to your success in Bio101/102 will be your ability to:
Defining a Good/Useful Scientific Hypothesis
A hypothesis is commonly understood to be an “educated guess”. But that is only part of a useful scientific hypothesis. A useful scientific hypothesis, simply put, is an explanation of phenomena that has predictive power.
It is important that a
scientific hypothesis is an
explanation that has or allows for a prediction. To
classify as such, a hypothesis must
include the premise on which the prediction is based. Thus many
hypotheses take
the generalized form of, “if __[such and
such]___is
true, then it follows that ___[this and that]___ will occur”. In this
way a
scientific hypothesis allows for falsifiability
– a fundamental
principle of the scientific method and hence scientific knowledge of
the world.
An Example of the
Scientific Method
As outlined above, the
scientific method often starts with a questions. Let's take the
following simple question as way of example:
According to the scientific method we should turn the question into a
hypothesis. Consider the following “educated
guess” about opening a water faucet.
If I open the faucet,
water will come out.
This statement fits the form of an if/then proposition and hence a hypothesis. But it does not give any underlying explanation of why the conclusion should be so. Why does it follow from opening a faucet that water will come out?
Now consider the following “scientific hypothesis” about opening a water faucet.
Opening a faucet creates an unobstructed path for water in a
pipe. If a
pipe contains water with a positive pressure on the water, then opening
the
faucet will result in water spilling out of the faucet. In the
following
experiment we will manipulate a series of faucets under varying
conditions to
test the validity of our hypothesis. In
a faucet without water, we predict that opening the faucet will not
result in
water spilling out. In a faucet with
water but under negative pressure, we predict that water will not spill
out. In a slightly open faucet with
water under positive pressure a small volume of water will spill out
slowly. And finally, in a completely
open faucet with water under positive pressure, a high volume of water
will
spill out rapidly.
On closer look, the previous example can be deconstructed as follows:
Hypothesis (premise/explanation/assumption):
Opening a faucet creates an unobstructed path for water in a pipe. If a pipe contains water with a positive pressure on the water, then opening the faucet will result in water spilling out of the pipe.
This is an if/then statement, but is in the form of a logical deduction. In this form, falsifiable predictions can be generated.
Prediction (expected results in a specific set of conditions):
In the following experiment we will manipulate a series of faucets under varying conditions to test the validity of our hypothesis. In an open faucet without water, we predict that opening the faucet will not result in water spilling out. In an open faucet with water but under negative pressure, we predict that water will not spill out. In a slightly open faucet with water under positive pressure a small volume of water will spill out slowly. And finally, in a completely open faucet with water under positive pressure, a high volume of water will spill out rapidly.
To further demonstrate the scientific process of looping back and forth between observation and interpretation, consider the following results of our hypothetical experiment.
Results:
In condition 1, water did not spill out of the open faucet without water. In condition 2, water did not spill out of the open faucet with water under negative pressure. In condition 3, a small volume of water did spill out of the slightly open faucet, but did so very rapidly – contrary to our predictions. Finally, in condition 4, a large volume of water did rapidly spill out of the completely open faucet. (See Table 1).
|
Table 1: Results of Water
Spilling out of Faucets under Varying Conditions |
|
|
Condition
1 – No water in pipes |
No
water |
|
Condition
2 – Water under negative pressure |
No
water |
|
Condition
3 – Water under positive pressure, slightly open faucet |
Low
volume of water spilling at high rate |
|
Condition
4 – Water under positive pressure, completely open faucet |
High
volume of water spilling at high rate |
Note: The results section has
written prose pointing out the important observations to the reader
along with a reference to a labeled Table that helps the reader "see"
the data.
Discussion (of hypothetical results):
All our predictions were confirmed except in the third condition, a small volume of water spilled out rapidly, rather than slowly. Considering this new observation a revised hypothesis is proposed. Opening a faucet creates an unobstructed path for water in a pipe. If a pipe contains water with a positive pressure on the water, then opening the faucet will result in water spilling out of the pipe. The amount of positive pressure on the water will be directly proportional to the speed at which water spills out of the faucet. In order to test this new hypothesis, we would like to apply varying degrees of pressure to water in a new series of pipes. An alternative hypothesis might take into account the degree to which a pipe is obstructed affects the rate at which water spills out. In this case, opening faucets in varying degrees should be combined with varying degrees of water pressure to determine the exact relationship. This information could be useful to anyone interested in plumbing or the factors in catastrophic failures of dams.
Note: Including an alternative hypothesis makes for a more complete discussion and respects the provisional nature of scientific knowledge. The final sentence in the “discussion” above is an example of placing the results in a larger context that is typical in scientific reporting. The implications of new observations are not always so obvious and thus it is important to help readers make relevant connections.
To Review – The take
home Message
Fundamental to your success in Bio101/102 will be your ability to: