1-In order to get real results, and a truly random study we need to not have bias. Its one of the things that I notice most when people are having their vaccine debate, or with political garb. You can almost always tell when someone has an agenda they are trying to push. 

2-An important feature of a good study is that the sample is randomly selected from the target population which is the entire group of individuals that the researcher is interested in studying. To choose randomly means that every member of the target population has an equal chance of being included in the sample. This will prevent biased in the sample group.

To prevent problems in obtaining a truly random sampling, several steps can be taken.

1. The      target population is well defined. If not well defined, the sample that is      actually studied may be outside the intended population or the survey may      include people that should be included.
2. The      sample matches the target population. It would be difficult to ask      everyone in the target population to provide the wanted information, so      the best that the researcher can do is select a subset of individuals from      the population and gather information from them.
3. The      sample size is large enough. If there is a large sample size that is      representative of the target population (randomly selected) the      information is likely to be accurate.

In any research project, steps must be taken to prevent biased. Part of that process is to realize the importance of random sampling. Bias can easily be introduced by not defining the target population well enough, ensuring the sample matches the target population and ensuring the sample size is large enough.

Reference:

Rumsey, D., (2010). Statistics Essentials for Dummies. Wiley Publishing, Inc. Indianapolis, IN

3-Sampling is the process of selecting a representative group from the population under study. It is more or less impossible to study every single person in a target population so psychologists select a sample or sub-group of the population that is likely to be representative of the target population we are interested in. If the sample we select is going to represent the target population then we need to make sure that the people in it are similar to the other members of the target population. This is important because we want to generalize from the sample to target population. The participants in research, the sample should be as representative as possible of target population. The more representative the sample, the more confident the researcher can be the results can be generalized to the target population. Everyone in the entire target population has an equal chance being selected. This is s similar to the national lottery. If the ‘population’ is everyone, who has bought a lottery ticket, then each person has an equal chance of winning the lottery. Random samples require a way of naming or numbering the target population and then using some type of raffle method to choose those to make up the sample. Random samples are the best method of selecting your samples from the population of interest. The advantages are that your sample should represent the target population and eliminate sampling unfairness, but the disadvantage is that it is very difficult to achieve.

     One of the  problems that can occur when selecting a sample from a target population is sampling bias, sampling bias refers to situation where the samples doesn’t reflect the characteristics of the target population. Many psychology studies have a biased sample because they have used a opportunity sample that comprises university students as their participants

Reference:

McLeod, S.A. (2014) .Sampling methods. Retrieved from www. simply psychology.org//sampling.html

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