Opening exercise
you want to know what proportion of the population likes rock music. you carefully consider three ways to conduct a study. what are the similarities and differences between the following
three alternatives? do any display clear advantages or disadvantages over the others?
a. you could pick a random sample of people and ask them the question, "do you like rock music? " and record their answers.
b. you could pick a random sample of people and follow them for a period of time, noting their music purchases, both in stores and online.
c. you could pick a random sample of people, separate them into groups, and have each group listen to a different genre of music. you would collect data on the people who display
an emotional response to the rock music.
a statistical study begins by asking a question that can be answered with data. the next steps are to collect appropriate data, organize and analyze them, and arrive at a conclusion in the
context of the original question. this lesson focuses on the three main types of statistical studies: observational studies, surveys, and experiments. the objective of an observational study
and a survey is to learn about characteristics of some population, so the data should be collected in a way that would result in a representative sample. this speaks to the importance of
random selection of subjects for the study. the objective of an experiment is to answer such questions as "what is the effect of treatments on a response variable? " data in an experiment
need to be collected in a way that does not favor one treatment over another. this demonstrates the importance of random assignment of subjects in the study to the treatments.
an observational study is one in which the values of one or more variables are observed with no attempt to affect the outcomes. one kind of observational study is a survey. a survey
requires asking a group of people to respond to one or more questions. (a poll is one example of a survey.) an experiment differs from an observational study. in an experiment,
subjects are assigned to treatments for the purpose of seeing what effect the treatment has on some response while an observational study makes no attempt to affect the outcomes
(i. e., no treatment is given). note that subjects could be people, animals, or any set of items that produce variability in their responses. here is an example of an observational study:
in a random sample of students, it was observed that those students who played a musical instrument had better grades than those who did not play a musical instrument. in an
experiment, a group of students who do not currently play a musical instrument would be assigned at random to having to play a musical instrument or not having to play a musical
instrument for a certain period of time. then, at the end of the period of time, we would compare academic performance.
classify each of the three study methods about rock music as an observational study, a survey, or an experiment.