A population is the entire group being studied, while a sample is a subset of the population that is selected for analysis. A hypothesis is a proposed explanation for a phenomenon that can be tested through research. There are two main types of hypotheses: the null hypothesis proposes there is no relationship between variables, while the alternative hypothesis proposes there is a relationship. Hypotheses can also be directional, predicting the nature of a relationship, or nondirectional, simply predicting a difference but not the direction.

1. Population
A population is the entire group that you want to draw conclusions about.

2. Sample
• In research terms a sample is a group of people, objects, or items that are
taken from a larger population for measurement. The sample should be
representative of the population to ensure that we can generalise the
findings from the research sample to the population as a whole.
• A sample is the specific group that you will collect data from. The size of
the sample is always less than the total size of the population.
• In research, a population doesn’t always refer to people. It can mean a group
containing elements of anything you want to study, such as objects, events,
organizations, countries, species, organisms, etc.

3. Hypothesis
• A hypothesis is a tentative answer to a research problem that is
advanced so that it can be tested.
• A hypothesis may be precisely defined as a tentative proposition
suggested as a solution to a problem or as an explanation of some
phenomenon (Ary, Jacobs and Razavieh, 1984). ... Hypothesis is a
tentative explanation that accounts for a set of facts and can be tested
by further investigation.

4. .A hypothesis (plural hypotheses) is a precise, testable statement of
what the researcher(s) predict will be the outcome of the study. It is
stated at the start of the study.
• A hypothesis is an assumption that is made based on some evidence.
This is the initial point of any investigation that translates the research
questions into predictions. It includes components like variables,
population and the relation between the variables. A research
hypothesis is a hypothesis that is used to test the relationship between
two or more variables.

5. This usually involves proposing a possible relationship between two
variables: the independent variable (what the researcher changes) and
the dependent variable (what the research measures).
• In research, there is a convention that the hypothesis is written in two
forms, the null hypothesis, and the alternative hypothesis (called the
experimental hypothesis when the method of investigation is
an experiment).

6. A fundamental requirement of a hypothesis is that is can be tested
against reality, and can then be supported or rejected.
• To test a hypothesis the researcher first assumes that there is no
difference between populations from which they are taken. This is
known as the null hypothesis. The research hypothesis is often called
the alternative hypothesis.

7. Types of research hypotheses
1) Alternative Hypothesis
The alternative hypothesis states that there is a relationship between the
two variables being studied (one variable has an effect on the other).
An experimental hypothesis predicts what change(s) will take place in
the dependent variable when the independent variable is manipulated.
It states that the results are not due to chance and that they are
significant in terms of supporting the theory being investigated.

8. 2) Null Hypothesis
• The null hypothesis states that there is no relationship between the two
variables being studied (one variable does not affect the other). There
will be no changes in the dependent variable due to the manipulation
of the independent variable.
• It states results are due to chance and are not significant in terms of
supporting the idea being investigated.

9. 3) Nondirectional Hypothesis
• A non-directional (two-tailed) hypothesis predicts that the independent
variable will have an effect on the dependent variable, but the
direction of the effect is not specified. It just states that there will be a
difference.
• E.g., there will be a difference in how many numbers are correctly
recalled by children and adults.

10. 4) Directional Hypothesis
• A directional (one-tailed) hypothesis predicts the nature of the effect of
the independent variable on the dependent variable. It predicts in
which direction the change will take place. (i.e. greater, smaller, less,
more)
• E.g., adults will correctly recall more words than children.