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Lesson 16: Does It Have a Trigger?

Lesson 16: Does It Have a Trigger?


Students will learn to identify and categorize survey questions versus sensor questions, and will practice writing sensor questions.


  1. Poster paper (one per student team)

  2. Sticky notes

  3. Sensor or Survey? handout (LMR_3.14_Sensor or Survey)


Participatory Sensing

Essential Concepts:

Essential Concepts:

A key feature that distinguishes the way sensors collect data from more traditional approaches is that sensors collect data when a 'trigger' event occurs. In Participatory Sensing, this event is something we humans agree upon beforehand. Every time that trigger happens, we collect data.


  1. Refer back to the list of sensors the class created during the previous lesson. Distribute a piece of poster paper to each student team, and have them create the following table:

  2. Assign each student team 3 sensors from the class’s list.

  3. Then, each team should complete the table using their knowledge of triggers discussed during the previous lesson. Remind students that when a trigger occurs, a sensor reacts to it and sends a signal to a data collector.

  4. Conduct a Gallery Walk of the posters. Each team will get to write one reaction or question about what they see on each poster.

  5. After the Gallery Walk, ask each team to return to their posters. If the posters include questions, have teams take turns responding to the questions.

  6. Quickwrite: In their DS Journals, ask student to respond to the following questions. They will have two minutes to write as much as they can:

    a. When you learned about survey questions, what were the two categories of questions you learned about? Answer: Open-ended and Closed-ended are the categories.

    b. What are some examples of these types of questions? Open-ended: write a paragraph, comments, essays, write a sentence, single answer. Closed-ended: multiple or single choice, yes/no, scales (e.g. 1-5), choose from a list, check a box.

  7. In teams, ask students to share their responses using the Give One/Get One strategy. You may use a timer to keep track of time.

  8. Remind students that one of the most important things they learned about sensors is that there is a trigger that reminds either a device or a person to answer a question or to collect data.

  9. For this class, students have already had experience with using sensors as a data collection tool – all the Participatory Sensing campaigns.

  10. Explain that survey questions are asked in Participatory Sensing campaigns. There is no difference in the type of questions that are asked when collecting data via surveys and when collecting data via PS campaigns.

  11. When deciding whether to use a survey or a PS campaign for data collection, we have to look at the research question of interest. Some questions are better answered with survey data, while others with PS campaigns. Research questions that include variation across time or across locations are good candidates for PS. Some questions might be answered by both.

    For example:

    Consider the research question: How does my sense of safety and security change as I go about my daily routine? This question would best be answered via a PS campaign because students could collect data in real time about their sense of security. A possible trigger could be "whenever you change locations" or "once at the start of every hour" or perhaps whenever a random alarm goes off.

    Consider the research question: What proportion of high school students are superstitious? This question could be done with a survey based on a random sample from the population of all high school students.

  12. Distribute the Sensor or Survey? (LMR_3.14) handout. In teams, students will determine whether a sensor or survey is better for a given research scenario.

  13. Once the teams have completed the handout, assign each team one research scenario from the Sensor or Survey activity.

  14. Conduct a Whip Around and have each team share their responses with the class. Allow students time to revise any incorrect responses.

  15. Summarize the lesson by highlighting that PS campaigns and surveys use similar questions. However, depending on the research topic of interest, the decision to use one or the other relies on whether or not a trigger is involved.

Class Scribes:

One team of students will give a brief talk to discuss what they think the 3 most important topics of the day were.


Suppose we wish to know more about whether people behave superstitiously. Write two research scenarios, using the following questions as a guide:

a. How would you collect data to address this using PS? Include the trigger event you would use, and the data you would like to collect when the trigger happens.

b. How would you collect data to collect this using a survey based on a random sample of people in California?

c. Describe the differences between these two approaches. What can you learn in one approach that you can't in the other?