Research Hypothesis
What Is a Real Hypothesis?
• A hypothesis is a tentative statement that proposes a
possible explanation to some phenomenon or event.
• A useful hypothesis is a testable statement which may
include a prediction.
• A hypotheses should not be confused with a theory.
• Theories are general explanations based on a large amount
of data.
• For example, the theory of evolution applies to all living
things and is based on wide range of observations.
• However, there are many things about evolution that are
not fully understood such as gaps in the fossil record.
• Many hypotheses have been proposed and tested.
What Is a Real Hypothesis?
• A hypothesis is an educated guess, based on
• Usually, a hypothesis can be supported or
refuted through experimentation or more
• A hypothesis can be disproven, but not proven
to be true.
What Is a Real Hypothesis?
• A scientific theory summarizes a hypothesis or
group of hypotheses that have been
supported with repeated testing. A theory is
valid as long as there is no evidence to dispute
it. Therefore, theories can be disproven.
Basically, if evidence accumulates to support a
hypothesis, then the hypothesis can become
accepted as a good explanation of a
phenomenon. One definition of a theory is to
say it's an accepted hypothesis.
What Is a Real Hypothesis?
• Example: If you see no difference in the cleaning ability
of various laundry detergents, you might hypothesize
that cleaning effectiveness is not affected by which
detergent you use.
• You can see this hypothesis can be disproven if a stain
is removed by one detergent and not another.
• On the other hand, you cannot prove the hypothesis.
• Even if you never see a difference in the cleanliness of
your clothes after trying a thousand detergents, there
might be one you haven't tried that could be different.
What Is a Real Hypothesis?
• A hypothesis (from Greek ὑπόθεσις) consists either of a
suggested explanation for a phenomenon or of a reasoned
proposal suggesting a possible correlation between
multiple phenomena.
• The term derives from the Greek, hypotithenai meaning "to
put under" or "to suppose."
• The scientific method requires that one can test a scientific
• Scientists generally base such hypotheses on previous
observations or on extensions of scientific theories.
• Even though the words "hypothesis" and "theory" are often
used synonymously in common and informal usage, a
scientific hypothesis is not the same as a scientific theory.
When Are Hypotheses Used?
• The key word is testable.
• That is, you will perform a test of how two variables
might be related.
• This is when you are doing a real experiment.
• You are testing variables.
• Usually, a hypothesis is based on some previous
• Any laboratory procedure you follow without a
hypothesis is really not an experiment. It is just an
exercise or demonstration of what is already known.
How Are Hypotheses Written?
• Chocolate may cause pimples.
• Salt in soil may affect plant growth.
• Plant growth may be affected by the color of the
• Bacterial growth may be affected by temperature.
• Ultra violet light may cause skin cancer.
• Temperature may cause leaves to change color.
How Are Hypotheses Written?
• All of these are examples of hypotheses because they use
the tentative word "may.".
• However, their form is not particularly useful. Using the
word may does not suggest how you would go about
proving it.
• If these statements had not been written carefully, they
may not have even been hypotheses at all.
• For example, if we say "Trees will change color when it gets
cold." we are making a prediction.
• Or if we write, "Ultraviolet light causes skin cancer." could
be a conclusion.
• One way to prevent making such easy mistakes is to
formalize the form of the hypothesis.
Research Hypothesis
• Every true experimental design must have this
statement at the core of its structure, as the
ultimate aim of any experiment.
• The hypothesis is generated via a number of
means, but is usually the result of a process of
inductive reasoning where observations lead to
the formation of a theory.
• Scientists then use a large battery of deductive
methods to arrive at a hypothesis that is testable,
falsifiable and realistic.
Research Hypothesis
• The research hypothesis is a paring down of
the problem into something testable and
• In the aforementioned example, a researcher
might speculate that the decline in the fish
stocks is due to prolonged over fishing.
• Scientists must generate a realistic and
testable hypothesis around which they can
build the experiment.
Research Hypothesis
• This might be a question, a statement or an
‘If/Or’ statement. Some examples could be:
– Is over-fishing causing a decline in the stocks of
Cod in the North Atlantic?
– Over-fishing affects the stocks of cod.
– If over-fishing is causing a decline in the numbers
of Cod, reducing the amount of trawlers will
increase cod stocks.
Research Hypothesis
• These are all acceptable statements and they all
give the researcher a focus for constructing a
research experiment.
• Science tends to formalize things and use the ‘If’
statement, measuring the effect that
manipulating one variable has upon another, but
the other forms are perfectly acceptable.
• An ideal research hypothesis should contain a
prediction, which is why the more formal ones
are favored.
Research Hypothesis
• A hypothesis must be testable, taking into account
current knowledge and techniques, and be realistic.
• A hypothesis must be verifiable by statistical and
analytical means, to allow a verification or falsification.
• In fact, a hypothesis is never proved, and it is better
practice to use the terms ‘supported’ or ‘verified’. This
means that the research showed that the evidence
supported the hypothesis and further research is built
upon that.
Research Hypothesis
• A hypothesis is important because it guides the
• An investigator may refer to the hypothesis to direct his
or her thought process toward the solution of the
research problem or subproblems.
• The hypothesis helps an investigator to collect the right
kinds of data needed for the investigation.
• Hypotheses are also important because they help an
investigator to locate information needed to resolve
the research problem or subproblems (Leedy and
Ormrod, 2001).
Research Hypothesis
• A hypothesis is a tentative expression of an
expected relationship between two variables.
• When a hypothesis is used, the purpose of the
study is to find out whether or not the hypothesis
is supported by the data.
• Several steps are involved in stating a hypothesis:
– Deriving the hypothesis from a theoretical framework;
– Designating the independent and dependent variables
in the hypothesis; and
– Stating the hypothesis.
Deriving a hypothesis
In order to state a hypothesis we have to have a
sound set of reasons for saying why we think the
hypothesis will be supported by some body of
This set of reasons is based on knowledge about
relationships among the variables that make up
the hypothesis.
Researchers refer to this rationale the theoretical
framework or the theory underlying the
Independent and dependent variables
• Hypotheses usually express a relationship
between two variables
• It is customary to designate one variable as
the independent and the other as the
dependent variable.
• The independent variable is assumed to be
the one responsible for changes in the other,
the dependent variable.
Independent and dependent variables
• Hypotheses generally express an expected
relationship between an independent and
dependent variable.
• To start, you can think of a hypothesis as a single
sentence with three parts:
– The subject, which generally is the independent
– A connecting verb, which defines the relationship
between the independent and dependent variables;
– The object, which is the dependent variable.
Hypothesis Test
• A hypothesis test is an assumption about a population
parameter. This assumption may or may not be true.
• The best way to determine whether a statistical
hypothesis is true would be to examine the entire
• Since that is often impractical, researchers typically
examine a random sample from the population.
• If sample data are not consistent with the statistical
hypothesis, the hypothesis is rejected.
• However, it is difficult for one to rove something to be
true and is much easier for one to prove something to
be not true
Hypothesis Test
• There are two types of statistical hypotheses.
• Null hypothesis. The null hypothesis, denoted
by H0, is usually the hypothesis that sample
observations result purely from chance.
• Alternative hypothesis. The alternative
hypothesis, denoted by H1 or Ha, is the
hypothesis that sample observations are
influenced by some non-random cause.
The null hypothesis for this study is:
• HO: As a result of the XYZ company employee
training program, there will either be no
significant difference in employee absenteeism or
there will be a significant increase.
which is tested against the alternative hypothesis:
• HA: As a result of the XYZ company employee
training program, there will be a significant
decrease in employee absenteeism
The null hypothesis for this study is:
• HO: As a result of 300mg./day of the ABC drug,
there will be no significant difference in
which is tested against the alternative
• HA: As a result of 300mg./day of the ABC drug,
there will be a significant difference in

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