1. Ask students to raise their hands if they have ever taken a survey. Then ask them to describe what a survey is.

Write responses on the board. Most students will have taken a survey or at least seen one. Guide students to discuss what surveys might ask about, who might administer them, and what the information might be used for.

Content Standard A:
Use appropriate tools and techniques to gather, analyze, and interpret data.

2. On the board, write the question, Do you play a sport? Ask only two or three students for a response to the question and write their responses on the board.

Ask only two or three students in a class of about 30. Ask only one or two students in smaller classes. This question is purposely general and should elicit a variety of answers, including, “Yes,” “No,” “Sometimes,” “Not now,” “I used to,” and “Basketball.” Write each student’s answer in a separate column.

3. Tell the class that you want to study physical activity patterns in students. On the basis of this information, ask students to get a more specific answer by either revising the question or asking a new question.

Write the new questions on the board below the original question. Ask the same students who answered the original question these new questions. Write their answers on the board in the appropriate column, below their answer to the first question.

Students may suggest asking additional questions such as, “Do you play a team or individual sport?”; “Which sport do you play?”; “Do you participate in a physical activity that is not considered a sport?”; or, “How often do you play?”

4. Return to the questions on the board. Select the answers from one student. Ask the class,

• “Do these answers from one person represent how all or most of the students in the class would respond?” (Does everyone agree with these answers?)
• “How many people would need to answer the question to represent how all or most of the students in the class would respond?”
• “Would the answers represent how all or most of the students in the school would answer the questions?”
• “Would the answers represent how middle school students in other schools in the city, state, or country would answer the questions?”
• “Would the answers represent how students in lower or higher grades would answer the questions?”

Students will probably realize that one person does not accurately reflect all students in the class, the school, the community, or in other grades. After a brief discussion of how many people it would take to provide an accurate representation, introduce the term sample size. Sample size is determined by two factors: the size of the population of interest, and how confident you need to be that your results are representative of that population. Sample size can be determined by mathematical formulas, which are beyond the scope of this curriculum. However, consider the following table that relates population size, confidence level, and sample size.

Data in this table demonstrate that the smaller the population, the larger the percentage of that population the sample size must be to be a representative sample. Make a transparency of this table if you believe it would help your students understand sample size.

Introduce the term representative sample when discussing which other groups may be represented accurately in a class survey. For example, students will probably recognize that first-graders would give very different answers from their own. Likewise, college students would give substantially different answers. Additionally, middle school students from different parts of the country, as well as from urban, rural, or suburban areas, would probably give different answers. Therefore, students need to be aware that a survey provides information about a specific population that may not be applicable to other groups. In other words, the group of people participating in the survey needs to be carefully defined to ensure that the survey is useful; then, a random sample within that population should be surveyed to avoid skewing the results.

5. Give each student a copy of Master 3.1, Survey. (If your school district requires parental permission for students to fill out surveys, you should have collected the Permission Letters by now.) Tell the students that they will now participate in a survey of physical activity behaviors of middle school students.

Students will answer questions about various forms of physical activity as well as influences on physical activity. Then they compare their class data with a larger database of all classes using this curriculum and with data derived from the national Add Health study in Activity 2.

Students should take the survey in a manner that respects and preserves their privacy. Their personal data remain anonymous in further activities. However, students should keep their surveys to make their own comparisons with data from other sources. As soon as students complete their surveys, they should either enter their data in the online database (for the Web version of this activity) or tally their information for the class (print version of this activity). In either case, students should move on to Activity 2 as soon as they complete their surveys.

Note to teachers: The student survey is part of an extensive national study of adolescents. In this study, the National Longitudinal Study of Adolescent Health (or Add Health study), over 20,000 students in grades 7 through 12 answered a very long survey in school, followed by three in-home interviews over the next eight years. The information provided in this curriculum supplement uses responses from over 6,000 seventh-grade students. The Add Health study uses a very large sample size and draws from a nationally representative sample. Data from the Add Health study have been used by epidemiologists around the country to investigate various aspects of adolescent behavior and health.

1. Tally the class data from the individual student surveys.

Write the number of students responding to each answer of each question on a transparency of Master 3.1, Survey.

2. Divide the class into groups of two to four. Give each group a copy of Master 3.3, Add Health Study Data, and each student a copy of Master 3.4, Class and Add Health Study Comparison.

3. Explain that each group will compare their class’s results with data from the Add Health study.

Each group of students will compare one question that has two possible answers (that is, no or yes questions) and one question that has four or five possible answers (that is, how many times questions). You may assign the questions or let the students select them.

Students should copy their class’s data onto their copy of Master 3.4, Class and Add Health Study Comparison, and answer the questions about their class’s data on the master. They will have to calculate the percentages for their class.

Tip from the field test: Be prepared to review how to calculate percentages.

Content Standard A:
Mathematics is important in all aspects of scientific inquiry.

4. Ask students to copy the Add Health data into the tables on Master 3.4. Then they will graph the percentages for each data set.

Students can use colored pencils to draw their bars on the graph. Make sure students label the legend on their graphs. On page 3 of Master 3.4, students should compare the data from the two data sources. They should also discuss the reasons for any difference in results between the two data sources. Allow approximately 15 minutes for students to complete Steps 3 and 4.

Note to teachers: The data are provided to students in two forms. Tables indicate both the actual number and the percentage of respondents who gave a particular answer. In the results from the Add Health study, the total number of respondents differs between questions. This is because respondents could choose not to answer questions or could select answers, such as “not applicable,” that are not available to students using the survey in this curriculum supplement.

5. Reconvene the class. Refer to Master 3.4, Class and Add Health Study Comparison, and ask students if they observed a difference between the data sets from the two sources for the same question. Why? Which data set do the students think is more accurate (or more representative of middle school students)?

Students will probably recognize differences between the data from the two sources. Remind the students about the concept of sample size. This should affect their decision about which data set is more accurate (or more representative).

6. In some cases, similar percentages may be observed for responses to the same questions on both data sets, although the numbers of respondents are very different. Why is this?

Students may observe similar percentages even though the numbers are very different. This indicates that the smaller samples are representative. Remind students of the concepts of sample size and representative sample if they do not bring them up in the discussion.