null and alternative

1. NULL AND ALTERNATIVE
HYPOTHESIS

3. NULL HYPOTHESIS-
 The null hypothesis is a general statement that states that there is no
relationship between two phenomenons under consideration or that
there is no association between two groups.
 A hypothesis, in general, is an assumption that is yet to be proved
with sufficient pieces of evidence. A null hypothesis thus is the
hypothesis a researcher is trying to disprove.
 A null hypothesis is a hypothesis capable of being objectively
verified, tested, and even rejected.
 If a study is to compare method A with method B about their
relationship, and if the study is preceded on the assumption that both
methods are equally good, then this assumption is termed as the null
hypothesis.
 The null hypothesis should always be a specific hypothesis, i.e., it
should not state about or approximately a certain value.
 The symbol for the null hypothesis is H0, and it is read as H-null, H-
zero, or H-naught.
 The null hypothesis is usually associated with just ‘equals to’ sign as
a null hypothesis can either be accepted or rejected.

4. PURPOSE OF NULL HYPOTHESIS-
 The main purpose of a null hypothesis is to verify/
disprove the proposed statistical assumptions.
 Some scientific null hypothesis help to advance a
theory.
 The null hypothesis is also used to verify the
consistent results of multiple experiments. For e.g.,
the null hypothesis stating that there is no relation
between some medication and age of the patients
supports the general effectiveness conclusion, and
allows recommendations.

5. ACCEPTANCE / REJECTION -
 When the p-value of the data is less than the significant level of the
test, the null hypothesis is rejected, indicating the test results are
significant.
 However, if the p-value is higher than the significant value, the null
hypothesis is not rejected, and the results are considered not
significant.
 The level of significance is an important concept while hypothesis
testing as it determines the percentage risk of rejecting the null
hypothesis when H0 might happen to be true.
 In other words, if we take the level of significance at 5%, it means
that the researcher is willing to take as much as a 5 percent risk of
rejecting the null hypothesis when it (H0) happens to be true.
 The null hypothesis cannot be accepted because the lack of
evidence only means that the relationship is not proven. It doesn’t
prove that something doesn’t exist, but it just means that there are
not enough shreds of evidence and the study might have missed it.

6. EXAMPLES-
 The following are some examples of null hypothesis:
 If the hypothesis is that “the consumption of a particular
medicine reduces the chances of heart arrest”, the null
hypothesis will be “the consumption of the medicine
doesn’t reduce the chances of heart arrest.”
 If the hypothesis is that, “If random test scores are
collected from men and women, does the score of one
group differ from the other?” a possible null hypothesis
will be that the mean test score of men is the same as
that of the women.
 H0: µ1= µ2
 H0= null hypothesis
µ1= mean score of men
µ2= mean score of women

7. ALTERNATIVE HYPOTHESIS
 An alternative hypothesis is a statement that describes that there is a
relationship between two selected variables in a study.
 An alternative hypothesis is usually used to state that a new theory is
preferable to the old one (null hypothesis).
 This hypothesis can be simply termed as an alternative to the null
hypothesis.
 The alternative hypothesis is the hypothesis that is to be proved that
indicates that the results of a study are significant and that the sample
observation is not results just from chance but from some non-random
cause.
 If a study is to compare method A with method B about their relationship
and we assume that the method A is superior or the method B is inferior,
then such a statement is termed as an alternative hypothesis.
 Alternative hypotheses should be clearly stated, considering the nature
of the research problem.
 The symbol of the alternative hypothesis is either H1 or Ha while using
less than, greater than or not equal signs.

8. PURPOSE OF ALTERNATIVE HYPOTHESIS-
 An alternative hypothesis provides the researchers with some
specific restatements and clarifications of the research
problem.
 An alternative hypothesis provides a direction to the study,
which then can be utilized by the researcher to obtain the
desired results.
 Since the alternative hypothesis is selected before conducting
the study, it allows the test to prove that the study is supported
by evidence, separating it from the researchers’ desires and
values.
 An alternative hypothesis provides a chance of discovering
new theories that can disprove an existing one that might not
be supported by evidence.
 The alternative hypothesis is important as they prove that a
relationship exists between two variables selected and that
the results of the study conducted are relevant and significant.

9. EXAMPLES
 The following are some examples of alternative
hypothesis:
 1. If a researcher is assuming that the bearing
capacity of a bridge is more than 10 tons, then the
hypothesis under this study will be:
 Null hypothesis H0: µ= 10 tons
Alternative hypothesis Ha: µ>10 tons
 2. Under another study that is trying to test whether
there is a significant difference between the
effectiveness of medicine against heart arrest, the
alternative hypothesis will be that there is a
relationship between the medicine and chances of
heart arrest.

12. THANK YOU
SUBSCRIBE FOR MORE