Why is it important that a sample be random For its validity

Why is it important that a sample be random? For its validity, all hypothesis testing depends heavily on the assumption that the sample that is used was drawn using probability sampling techniques. What can you do if you just cannot use a probability sampling technique. Provide an example of a population, and explain how you would collect a random sample from that population.

Solution

Selecting a sample randomly, means that all the elements from which samples are choosen will have the same probability of being selected during the sampling process. selecting samples at random can also be called as unbaised sampling(since we are not differentiating between the elements for selectoin)

There are several technoques that can be followed when we cannot use probability sampling technique, which are all grouped under the name non-probability sampling technique.

non-probability sampling technique include techniques like

example of a population : populations which include drug addicts, homeless people, individuals with STD(AIDS/HIV), those who download illegal content from internet and so forth on whome reasearch activities are to be conducted. Such populations can be hard to reach and/or hidden because of the way the society looks on to them.

Following Self-sampling technique, we could expect certain number of samples(in our case, individuals on whom tests are to be conducted) to admit themself voluntarily, but this sample size might not be sufficient, then we can ask those who agreed to be part to help identify others that might be willing to take part