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 observation.

• Usually, a hypothesis can be supported or refuted through experimentation or more observation.

• 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 hypothesis.

• 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

observation • 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

light. • 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 falsifiable.

• 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 research. • 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 data. 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 hypothesis.

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 variable; – A connecting verb, which defines the relationship

between the independent and dependent variables; and – 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 population.

• 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.

Example

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

Example

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 depression.

which is tested against the alternative hypothesis:• HA: As a result of 300mg./day of the ABC drug,

there will be a significant difference in depression.