What Are The Disadvantage Of Random Sampling?

A primary disadvantage of random sampling is that it may not in fact be a random sample.   Therefore conclusions or interpretations of the sample data could be misleading and the consequences severe, such as death.   For example, a random sample of 100 individuals with cancer are selected to test a new cancer fighting drug.    The results of those sampled indicate the drug did reduce the risks of the cancer and in some cases the cancer went into remission.    However, if this drug were put on the market to treat 1,000,000 people with this particular cancer the side effect of "instant death" that did not appear in the original sample of 100 because none of the original 100 died would make this drug unacceptable if the sample had identified this fact.   Lets say the death rate was only 1% this would mean 10,000 people out of the 1,000,000 if treated with the new medicine would die instantly.  

Random sampling also could create costly repairs or expose individuals to dangerous situations.   For example, recall notices from automobile manufacturers are common place today, however, if full or first article testing were done instead of sample testing some of these recalls would be unnecessary.   The cost of recalls could well exceed the cost of full sampling in these situations.  

In random sampling, researchers draw a sample from the population randomly so that every element in the population has an equal chance to be selected.  However, the assumption that 'randomly' walking upto people in a street produces a sample that is representative of the whole city is often wrong. For one thing,, any street, whether in a rich neighbourhood or a poor one, contains more of the same kinds of people than others. Secondly, Any researcher is apt to find some people more approachable than others, which is yet another bias. But then snowball sampling also has its disadvantages and random sampling definitely offers a considerable savings in time and expense.

Complete disadvantages of random sampling