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Unit 3 Concept map (Observational studies vs Experiments (Experiments: In…
Unit 3 Concept map
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Sampling Error- A piece of data that cannot be correct due to the sample being taken not being reflected of the whole population.
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Voluntary Response Variable- A sample that consists entirely of volunteers. However, these samples are always biased.
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Good Sampling Tecniques
Stratified SRS: First you divide the population into "strata". There can be any number of these. Then choose a simple random sample from each stratum. Combine those into the overall sample.
Advantage: An advantage of a stratified SRS is similar to a cluster however it is a more randomized group, taken from each subgroup to get a very accurate data set. So and advantage is that your data is not biased or skewed to one group it is very even.
Disadvantage: If you are trying to find patterns in a specific group this tecnique would not be very useful because of how random it is, and how it selects samples from each inner group of a population.
Cluster Sampling: the researcher divides the population into separate groups, called clusters. Then, a simple random sample of clusters is selected from the population.
Advantage: You get an even more accurate data set because you are randomly sampling 2 parts of the population
Disadvantage: The data can be skewed because you can be taking data from one group and not spreading it out. For example you can just be picking people from one section of a stadium, but due to their position in the stands they could share commonalities like salaries. It is not the most accurate of tecniques
SRS: A simple random sample is a subset of a statistical population in which each member of the subset has an equal probability of being chosen.
Advantage: One advantage of having your population sample to be completely random is that there is little to no risk of bias or skewed data.
Disadvantages: If you want to favor one group of a population in your experiment it is impossible because of the randomness
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Blinding: Typically used to describe the awareness of patients or the doctors as to if they are receiving the placebo or the actual treatment.
Placebo Effect: As before mentioned, a placebo is a fake pill or type of treatment that does not have any affect on the patient physically. However, after being asked how the patient feels they will often say that their symptoms have improved, even if they were prescribed the placebo. This is called the placebo effect.
Samples and Surveys 
Example: An assembly room isn a high school is set up completely randomly of students. If you would want to find out how many people ate breakfast out of the assembly you could take a cluster of people in the front row and gather the data. You could also take a sample of the people in the bottom rows middle rows and upper rows, to get a more diverse group of people.