Unit 8, Lesson 2
Study Types
Algebra 2
2.1
Warm-up
Standards Alignment
Building On
Addressing
HSS-IC.B.3
Recognize the purposes of and differences among sample surveys, experiments, and observational studies; explain how randomization relates to each.
Building Toward
Instructional Routines
NoneMaterials
NoneActivity Narrative
This Warm-up prompts students to compare four questions. It gives students a reason to use language precisely (MP6) and provides the opportunity to compare characteristics of the given items. Monitor for students who mention numerical and categorical data, as well as those who refer to the variability of the data to determine whether the question is statistical.
Launch
Arrange students in groups of 2–4. Display the questions for all to see. Give students 1 minute of quiet think time and then time to share their thinking with their small group.
Activity
NoneFor each question, determine whether it is a statistical question. If it is a statistical question, determine whether an experimental study, observational study, or survey would be best at providing data to answer the question. Explain your reasoning.
- Do dogs who eat only Brand A of dog food have more health problems than those who eat a variety of food brands?
- Do people who sit for at least 8 hours per day have more health problems than those who sit for fewer than 8 hours per day?
- Which brand of dog food has the most protein per serving?
- Do people who play card games feel healthier than those who do not?
Student Response
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Building on Student Thinking
Activity Synthesis
Record and display the responses for all to see. There is no single correct answer to the questions, so attend to students’ explanations, and ensure the reasons given are correct.
During the discussion, ask students to explain the meaning of any terminology they use, such as “survey study,” “statistical question,” “observational study,” or “experimental study.”
Here are some questions for discussion.
- “What is a statistical question?” (a question that requires data to be collected, and in which variation is expected in the data collected)
- “What is the difference between an observational study and an experimental study?” (In an observational study, we collect the data without influencing subjects directly to answer our question. In an experimental study, we directly influence one variable and collect data to answer our question.)
- “What makes a survey a special type of observational study?” (In a survey, the researcher asks people questions, and their responses are the data. In other observational studies, the researcher observes people, and the information the researcher records about the observations becomes the data.)
2.2
Activity
Materials
NoneActivity Narrative
In this activity, students take turns with a partner recognizing the purposes of and differences among sample surveys, experiments, and observational studies. Students trade roles explaining their thinking and listening, providing opportunities to explain their reasoning and critique the reasoning of others (MP3).
Launch
Arrange students in groups of 2. Tell students that, for each question, one partner determines if a survey, observational study, or experimental study would be the best way to collect data to answer the question. The partner’s job is to listen and make sure they agree. If they don’t agree, the partners discuss until they come to an agreement. For the next question, the students swap roles. If necessary, demonstrate this protocol before students start working.
Display the statements for all to see.
- Surveys are sets of questions given to people to seek their responses.
- Observational studies collect data without influencing subjects directly.
- Experimental studies collect data by directly influencing one variable to determine how another variable is changed.
MLR8 Discussion Supports. Students should take turns finding a match and explaining their reasoning to their partner. Display the following sentence frame for all to see: “I noticed , so I matched .” Encourage students to challenge each other when they disagree.
Advances: Speaking, Conversing
Advances: Speaking, Conversing
Action and Expression: Internalize Executive Functions. To support development of organizational skills in problem-solving, chunk this task into more manageable parts. For example, encourage students to select the questions in any order.
Supports accessibility for: Organization, Attention
Supports accessibility for: Organization, Attention
2.3
Activity
Instructional Routines
MLR6: Three ReadsMaterials
NoneActivity Narrative
The mathematical goal of this activity is for students to understand the purposes of and differences among sample surveys, experiments, and observational studies, and to apply that knowledge in context. Students also have the chance to discuss how to interpret the results from a survey, including whether a causal relationship is likely present based on the study’s methods.
This activity uses the Three Reads math language routine to advance reading and representing as students make sense of what is happening in the text.
Launch
Arrange students in groups of 2.
Use Three Reads to support reading comprehension and sense-making about this problem. Display only the problem stem, without revealing the questions.
- For the first read, read the problem aloud, and then ask, “What is this situation about?” (a study of how much television people watch) Listen for and clarify any questions about the context.
- After the second read, ask students to list any quantities that can be counted or measured. (the number of people in the study, the survey questions)
- After the third read, reveal the questions and ask, “What are some ways we might get started on this?” Invite students to name some possible starting points, referencing quantities from the second read. (Consider characteristics of each type of study, then think about if there could be other causes for lower energy.)
Lesson Synthesis
The purpose of this discussion is for students to associate the appropriate type of study with the conditions surrounding the question of interest.
Here are some questions for discussion:
- “What type of study would you perform to test if one weight-lifting routine results in building strength faster than another weight-lifting routine? Explain your thinking.” (I would use an experimental study because I want to compare two different routines, the first variable, to how fast strength builds, the second variable. I might also want a control group that does not do any weight lifting. If I already had two groups using each routine, I could potentially do an observational study to see which group gains strength faster.)
- “What type of study would you conduct if you wanted to know how many hours high school students spend gaming on school nights? Explain your reasoning.” (I would do a survey and ask students how much time they spend gaming on weeknights.)
- “Describe an example of an observational study.” (Investigate the percentage of people who come to a complete stop at stop signs by standing at an intersection that has a stop sign and observing the number of cars that come to a complete stop.)
- “Could the example given for the observational study be investigated with a survey? Explain your thinking.” (It could be, but I would have to change the question to the percentage of people who say they come to a complete stop at stop signs.)
- “Could the example given for the observational study be investigated with an experimental study? Explain your thinking.” (An experimental study does not make sense because I’m not comparing how one variable relates to another variable.)
Student Lesson Summary
Three of the best ways to collect data are through surveys, experimental studies, and observational studies. Each method has advantages and disadvantages, depending on the question we are trying to answer.
A statistical study begins with a research question, which clearly describes what we want to know. Most research questions are questions about characteristics of a population or about the effect of one variable on another.
Sometimes researchers have a question about a population, like: “What percentage of the fish in Lake Erie are toxic for humans to eat?” Sometimes researchers have a question about how two or more populations compare, like: “Which lake, Lake Erie or Lake Ontario, has a higher percentage of fish that are toxic for humans to eat?” And sometimes, researchers want to change one variable and see how a population responds. For example, “Does taking a fish oil supplement daily help older adults maintain brain function?” After the research question is created, the researcher needs to collect some data.
There are three methods for collecting data: observational studies, surveys, and experimental studies. In an experimental study, the researcher deliberately does something to one or more groups of individuals, such as giving them access to tutoring or giving them a vitamin, and then measures their responses in comparison to another group that does a different thing, such as not going to tutoring or taking a different type of vitamin. This is different from observational studies and surveys, in which the researcher collects data about individuals as they are.
In an observational study, the researcher records values for one or more variables, like ZIP code or height, for each individual participating in the study. These values can be obtained by observation, measure, or taken from existing data that has already been collected (like the U.S. census).
A researcher can also collect data with a survey, in which they ask each participant to answer one or more questions.
Each method comes with advantages and limitations that the researcher must understand before planning a study. The method used to collect data also affects what kind of conclusions can be drawn. Choosing the best method for a research question takes careful thought and practice.