21. sat/act a researcher studies differences ...
21. sat/act a researcher studies differences in career goals between boys and girls in middle school. all of the students in the seventh grade schools in a particular county answer a list of questions. what type of study is this? ① experiment ② sample survey ③ observational study ④ random trial\n22. performance task a grocery store surveys every fifth customer to determine whether it should consider expanding its organic foods department. the results of the 500 customers surveyed are shown in the table.\npart a what type of sampling method was used? does it seem valid?\npart b based upon the results of this survey, about what percent of the store’s customers would favor the expansion?\npart c what is the statistical variable in this study? is this a quantitative or categorical variable?\nin favor of expanded organic dept.?\nyes 378\nno 97\nindifferent 25
Answer
# Explanation:
## Step1: Identify study type in 21
The researcher just collects data on existing career - goals without manipulating any variables. So it's an observational study.
## Step2: Identify sampling method in 22 Part A
Surveying every fifth customer is a systematic sampling method. It can be valid if the order of customers has no hidden pattern related to the opinion on organic department expansion.
## Step3: Calculate percentage in 22 Part B
The number of customers in favor is 378 out of 500. The percentage is $\frac{378}{500}\times100\% = 75.6\%$.
## Step4: Identify variable type in 22 Part C
The variable is "opinion on expanding the organic foods department" (yes/no/indifferent). It is a categorical variable as it represents different categories of responses.
# Answer:
21. C observational study
22. Part A: Systematic sampling, may be valid.
Part B: 75.6%
Part C: The statistical variable is "opinion on expanding the organic foods department", it is a categorical variable.