Answer:
the change in birth and death rates
Explanation:
To provide a greater certainty that the observed results are not by chance.
Answer:
an implicit rule
Explanation:
An implicit rule or idea is the general communication or understanding by the people which is not directly stated or conveyed but is understood by the moral conscience.
It is not directly stated or said but is understood by civic sense.
Thus people who understands that they have to form a line and wait for their turn is an example of an implicit rule.
