2. Hypothesis???
+Represents what the researchers
think will happen in an experiment.
+Is a prediction, but it involves
more than a guess. (Predictions
about what your research will
find).
+It doesn’t have to be correct.
+Is a statement that can be tested
by scientific research.
3. Valid or Not???
Statements Comments
Briar’s Aspirin cures headaches faster than RCS Aspirin. Valid hypothesis. Can be checked by using the two forms of
aspirin on randomly chosen populations of headache sufferers.
Eating two ounces of olive oil a day decreases the odds of
contracting heart disease.
Valid hypothesis. Can be checked by randomly assigning large
numbers of people diets that contain or do not contain two
ounces of olive oil and monitoring their health over long periods
of time.
The gravitational force between two masses is proportional to
the products of the masses and decreases exponentially with
the distance between the masses.
Valid hypothesis. Also false, since gravitational force decreases
as the square of the distance, not as the exponential.
If electrons were 10% less massive, no life would exist in the
universe.
Fascinating statement, but not a valid and testable hypothesis,
particularly since it is impossible to anticipate all forms that life
could take.
A Toyota Camry weighs exactly 1000 kg. This is a valid hypothesis, but it is silly if left as a hypothesis.
There is no reason that the weight of a car should come out to
be such a neat round number.
What is the best fertilizer to use to get large and tasty tomatoes? Not a valid hypothesis. Hypotheses have to be definite
statements and cannot be questions.
Macs are better than PCs. Not a valid hypothesis. It is impossible to imagine evidence that
could sway the enthusiastic supporters of each kind of computer
to accept the other as better.
4. Creating a Hypothesis
+ Researchers might draw a hypothesis from a specific theory or
build on previous research.
Important things to consider:
1. State the problem that you are trying to solve. (Make sure that
the hypothesis clearly defines the topic and the focus of the
experiment).
2. Try to write the hypothesis as an if-then statement. (Template: If
a specific action is taken, then a certain outcome is expected).
3. Define the variables.
5. Good Hypothesis
+Is your hypothesis based on your research on a topic?
+Can your hypothesis be tested?
+Does your hypothesis include independent (changes or
controls) and dependent (observes and measures) variables?
Daily apple consumption leads to fewer doctor’s visits.
6. Hypothesis-driven experiments
+Your experiment should have at least one control or
independent variable, and at least one response or dependent
variable
Alternative hypothesis vs Null hypothesis
• The null hypothesis is usually that changes in your independent variable will not lead to
any significant changes in your dependent variable.
• The hypothesis that changing the first variable does change the second is called the
alternative hypothesis.
7. Test a hypothesis
State a hypothesis
Design an experimental procedure to test the
hypothesis
Construct any necessary apparatus
Perform the experiments
Analyse the data from the experiment to
determine how likely it is the hypothesis can
be disproved
Refine or correct the hypothesis and
continue if necessary
8. Hypothesis examples
Research question Hypothesis Null hypothesis
What are the health benefits of
eating an apple a day?
1 2
Which airlines have the most
delays?
3 4
Can flexible work arrangements
improve job satisfaction?
5 6
What effect does daily use of
social media have on the
attention span of under-16s?
7 8
A
There is no relationship
between social media
use and attention span
in under-16s.
E
There is a negative correlation
between time spent on social
media and attention span in under-
16s.
G
There is no
relationship
between working
hour flexibility and
job satisfaction.
D
Employees who have
flexible working hours
will report greater job
satisfaction than
employees who work
fixed hours.
B
Low-cost airlines are
more likely to have delays
than premium airlines.
H
Low-cost and
premium airlines
are equally likely to
have delays.
C
Increasing apple consumption in
over-60s will have no effect on
frequency of doctor’s visits.
F
Increasing apple consumption in
over-60s will result in decreasing
frequency of doctor’s visits.
