Examples:
SITUATION A: A medical researcher is interested in finding out whether a new medication will have any undesirable side effects. The researcher is particularly concerned with the pulse rate of the patients who take the medication.
Since the researcher knows that the mean pulse rate for the population under study is 82 beats per minute, the hypothesis for the situation are:
H0 μ = 82 and
H1 μ ≠ 82
The null hypothesis specifies that the mean will remain unchanged, and the alternative hypothesis states that it will be different. this test is called a two-tailed test, since the possible side effects of the medicine could be raise or lower the pulse rate.
SITUATION B: A chemist invents an additive to increase the life of an automobile battery. If the mean lifetime of the automobile battery is 36 months, then his hypothesis are:
H0 μ ≤ 36 and
H1 > 36
In this situation, the chemist is interested only in increasing the lifetime of the batteries, so his alternative hypothesis is that the mean is greater than 36 months. The null hypothesis is that the mean is less than or equal to 36 months. This test is called right tailed test, since the interest is an increase only.
SITUATION C: A constructor wishes to lower heating bills by using a special type of insulation in houses. If the average of the monthly heating bills is Php78, her hypothesis about heating costs with the use of insulation are:
H0 μ ≥ Php78 and
H1 μ < Php78
The test is a left tailed test, since the constructor is interested only in lowering heating costs.
By: Andrea Beatrice Pechueco
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