This lesson consists of three activities and should take three class periods to complete. In the first activity, students are introduced to surveys and survey questions. They consider the concepts of sample size and representative samples. Students then participate in a survey of physical activity. In the second activity, students investigate how social and behavioral scientists can use a survey to study behavior. They compare data from their class’s surveys, from surveys submitted by all classes using this curriculum, and from a national survey (the National Longitudinal Study of Adolescent Health, or Add Health study) to further explore the concepts of sample size and representative sample. Finally, in the third activity, students use data from the Add Health study to design and answer research questions about relationships between influences on behavior and physical activity.
Surveys are important tools for social and behavioral scientists. They can provide quantifiable information about behaviors and behavior trends and allow scientists to study the relationships among different influences and behaviors. Survey questions must be designed carefully so that they are very specific. Sample size and a representative sample are critical to generate useful data from a survey. Different influences can affect a person’s physical activity levels.
After completing this lesson, students will
See the following section in Information about the Science of Healthy Behaviors:
|Activity||Master||Number of copies|
|1||Master 3.1, Survey
|1 copy per student
1 copy per student if required by school district
|2 (Web version)||Master 3.2, Comparison Guide||1 copy per student and 1 transparency|
|2 (print version)||Master 3.1, Survey
Master 3.3, Add Health Study Data
Master 3.4, Class and Add Health Study Comparison
| 1 transparency
1 copy per student team and 1 transparency
1 copy per student and 1 transparency
|3 (Web version)||Master 3.5, Analysis Guide||1 copy per student and 1 transparency|
|3 (print version)||Master 3.5, Analysis Guide
Master 3.6, Influences on Physical Activity Behaviors
| 1 copy per student and 1 transparency
1 copy per student team and 1 transparency
If your school district requires parental consent for students to fill out surveys, please distribute and then collect signed copies of the Permission Letter master at the end of the supplement, after Master 5.2. Otherwise, no preparation is necessary.
If you are using the Web version of this activity, you must establish a unique class code for each class that will enter data into the Web database. To do this, go to the URL http://science.education.nih.gov/supplements/healthy/student. This is a menu page from which you can access the Teacher Administration page by clicking on “Lesson 3—Database Administration.” The Database Administration page is for teachers only and allows you to register your classes and create a unique identifier for each class data set. Enter the user name healthyadmin and the password admin, and then click “Sign In” to enter this site and register your classes. Write down the class code(s) that appear on screen. The class code(s) will also be sent to you by e-mail. Verify that the computer lab is reserved for your classes for Activities 2 and 3 or that classroom computers are ready to use.
If you are using the print version of this activity, no other preparation is needed.
Same as for Activity 2.
For classes using the Web or print versions of this activity:
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.
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.
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?”
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.
|Sample Size Needed for||Population Size*|
|90 percent confidence||27 (90%)||73 (73%)||214 (21.0%)||258 (0.05%)||265 (0.03%)||271 (0.01%)|
|95 percent confidence||28 (93%)||79 (79%)||278 (28.0%)||357 (0.07%)||370 (0.04%)||381 (0.01%)|
|99 percent confidence||29 (97%)||87 (87%)||399 (40.0%)||586 (0.12%)||622 (0.06%)||655 (0.01%)|
|*Sample size as a percent of population size is in parentheses.|
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.
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.
For classes using the Web version of this activity:
Note to teachers: You will need to examine your school’s computer and Web resources to determine the most effective way to enter data into the database. Can an entire class get computer access and enter data simultaneously? Can small groups access a few computers while the remainder of the class is working on other tasks? One option is to have students fill out the survey on paper and then have one person enter the data. To protect students’ privacy, remind students not to write their names on the survey.
It will save time to have the computers online and at the correct URL: http://science.education.nih.gov/supplements/healthy/student. This is a main menu page from which you and students can access this activity. Students will need the class code you established for their class to access the Activity 2—Data Entry and Activity 2—Analyzing the Survey Results menu pages.
We recommend that the survey and the discussion of the use of the database be completed during class. Students can then generate reports during class or, if necessary, from home.
You may want to demonstrate for students how this is done to ensure that data entry proceeds smoothly and quickly.
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 students select them.
The number of respondents, percentages, and the graphs from the all-classes database and Add Health database are provided for students online. Results are presented in table and bar-graph formats. Students should copy their class’s data onto their copy of Master 3.2, Comparison Guide, make the calculations for their class, and draw the corresponding bar graph. Students should then answer the questions on the master. Students can use colored pencils to draw the bars on their graph. Make sure students label the legend on their graph. Students should compare the data they get from all three data sources. They should also discuss the reasons for any difference or lack of difference in results among data sources. Allow approximately 15 minutes for completion of this step.
Tip from the field test: Be prepared to review how to calculate percentages.
Note to teachers: The data are provided to students in two forms. Tables generated for each question include both the actual number and the percentage of respondents who gave each answer. The all-classes database includes all classes that have taken the survey as part of The Science of Healthy Behaviors curriculum supplement and entered these data online. In the data 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.
Students will probably observe differences among the data from the three sources.
Remind students about the concept of sample size. This should affect their decision about which data set is the most accurate (or most representative of middle school students).
Note to teachers: Initially, results from all classes entering survey data may be very similar to results from individual classes. Over time, however, results from all classes using this supplement will grow larger and more representative and should become similar to the results from the Add Health study.
Students may observe similar percentages even though the numbers are very different. This indicates that the smaller samples are representative. Remind the students of the concepts of sample size and representative sample if they do not bring them up in the discussion.
Tip from the field test: Students are familiar with making scientific measurements in a laboratory. This is a good time to point out to students that human behavior also can be measured and studied scientifically.
Write the number of students responding to each answer of each question on a transparency of Master 3.1, Survey.
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.
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.
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).
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.
Next: Lesson 3 (Page 2 of 2)