If any of the steps is missed then statistics is used inappropriately. For example: a research is done to test the effect of medicine A in curing a particular disease. Two groups of people are selected with both the groups having that particular disease. But the first group is of people aged 20-30 and the second group is of people aged 60-70. The first group is given the medicine while the second group is given placebo and then they are observed for a long period of time. It is found that first group has cured more rapidly. But from this we cannot conclude that medicine A has better effect in curing the medicines because the ages of people in the groups are different. People aged 20-30 have generally better immunity power than people aged 60-70. Hence this result is biased. Both the...