Question

independent practice
a statistics student wants to determine the average amount of money spent by college students each week.
to collect their data, the student gives a survey to 20 classes and has every student in the class take the survey.
what important factor was left out of this study?
treatment group
randomization
control group
placebo

Explanation:

When conducting a study to determine the average amount of money spent by college students each week, randomization is crucial. Randomization helps ensure that the sample is representative of the entire population of college students. In this case, by only surveying 20 classes (and every student in those classes), the student may be introducing bias. For example, certain classes may have students with different spending habits (e.g., a business - related class may have students with more disposable income if they have internships compared to a liberal - arts class). A treatment group is used in experiments where a treatment is administered, which is not the case here. A control group is also for experiments (to compare the treatment effect). A placebo is used in medical or psychological experiments where a fake treatment is given. Since this is a survey - based study (not an experiment), treatment group, control group, and placebo are not relevant. Randomization, which helps in getting an unbiased sample, is the important factor left out.

Answer:

Randomization