Samples and Surveys
S.IC.1 Understand statistics as a process for making inferences to be made about population parameters based on a random simple from that population
S.IC.3 Recognize the purposes of and differences among sample surveys, experiments, and observational studies; explain how randomization relates to each
Objective: To identify sampling methods. To recognize bias in samples and surveys
3 Main Types of Studies
Sample Survey
Ask members of a sample group of population the same set of questions
Experiment
Applying a treatment to a group of people and measuring against a group of people not given the treatment
Observational Study
Observing members of a sample of a population in a way that they are not affected by the study
A population is all the members of a set. A sample is part of a population. If you determine a sample carefully, the statistics for the sample can be used to make general conclusions about the larger population.
There are various sampling types and Methods such as,
Convenience Sample: select any members of the population who are conveniently and readily available.
Self-selected sample: select only members of the population who volunteer for the sample.
Systematic sample: order the population in some way, and then select from it at regular intervals.
Random sample: all members of the population are equally likely to be chosen.
Samples vary in how well they reflect a population. A sample has a bias when a part of a population is overrepresented or underrepresented. A bias is a systematic error introduced by the sampling method.