Question

decide if each of the following studies is an example of an observational study, an experimental study, or a statistical survey. 1. a researcher polls a sample of high school seniors to determine the numbers of hours of sleep they get during the week. he uses these answers to examine whether there is a correlation between lack of sleep and bad grades. 2. teachers in two second grade classrooms use different teaching methods to teach a mathematical concept to their students. they then compare the successes of their students on a common test. 3. a questionnaire concerning the quality of food in the cafeteria is distributed to students and staff in the cafeteria is distributed to students and staff in a high school. results of the survey members at a high school. results of the survey are used to make improvements in the cafeteria. 4. in order to study its customer service, a bank hires an observer to record the number of minutes that each customer waits in line at the local bank between the hours of noon and 1 pm. 5. a group of adult women with high cholesterol are divided into two groups in a research project concerning a new cholesterol medication. one group is given the new medication while the second group receives a placebo. after a month, the cholesterol levels of the two groups are reevaluated. 6. every 50th box of crackers on an assembly line is pulled from the line and weighed to determine if the true weight is consistent with what the package label states.

Explanation:

1.

研究者通过问卷调查（polls a sample）收集高中生的睡眠时长数据，以研究睡眠不足和成绩差的相关性，没有干预变量，属于统计调查（statistical survey），因为是通过收集现有数据（学生的回答）来分析关系，不是观察或实验干预。

两位老师使用不同教学方法（不同处理）教数学概念，然后比较学生测试成绩，属于实验研究（experimental study），因为有对教学方法（自变量）的干预，分组（两个班级）并施加不同处理来观察结果（测试成绩）。

通过向学生和教职工分发问卷（questionnaire）来收集关于食堂食物质量的反馈，用于改进食堂，属于统计调查（statistical survey），是通过问卷收集数据来了解情况，无干预或观察行为的记录。

Answer:

statistical survey

2.