options: Make inferences and justify conclusions from sample surveys, experiments, and observational studies.

Use random sampling to draw inferences about a population.

Understand and evaluate random processes underlying statistical experiments.

Use the rules of probability to compute probabilities of compound events in a uniform probability model.

Interpret linear models.

Understand independence and conditional probability and use them to interpret data.

Investigate patterns of association in bivariate data.

Calculate expected values and use them to solve problems.

Investigate chance processes and develop, use, and evaluate probability models.

Use probability to evaluate outcomes of decisions.

Summarize, represent, and interpret data on two categorical and quantitative variables.

Summarize, represent, and interpret data on a single count or measurement variable.

Develop understanding of statistical variability.

Summarize and describe distributions.

Draw informal comparative inferences about two populations.
problem_activity: Warm-up
This warm-up encourages students to analyze the structure and value of expressions, and to connect them to the process of calculating a mean.  Each expression has one obvious reason it does not belong, however, there is not one single correct answer.
As students discuss in small groups, listen for ideas related to finding the mean of a data set. Highlight these ideas during whole-class discussion.
Launch
Arrange students in groups of 2–4. Display the expressions for all to see. Give students 1 minute of quiet think time, and ask them to indicate when they have noticed one expression that does not belong and can explain why. When the minute is up, ask them to share their thinking with their small group, and then, together, find at least one reason each expression doesn't belong.
Student Facing
Which expression does not belong? Be prepared to explain your reasoning.
\(\displaystyle \frac {8+8+4+4}{4}\)
\(\displaystyle \frac {10+10+4}{4}\)
\(\displaystyle \frac {9+9+5+5}{4}\)
\(\displaystyle \frac {6+6+6+6+6}{5}\)
Student Response
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Activity Synthesis
Ask each group to share one reason why a particular expression does not belong. Record and display the responses for all to see. After each response, ask the class if they agree or disagree. Since there is no single correct answer to the question, attend to students’ explanations and ensure the reasons given are reasonable. If students give unsubstantiated claims, ask them to substantiate them.
At the end of the discussion, ask students which expression or expressions most represent how they would find the mean of a data set. There is a reason each expression (other than C) could represent how they would find the mean of a data set, however, highlight reasoning about the number of terms in the numerator being the same as the value of the denominator (e.g., there are 5 terms in the numerator and the denominator is 5).


correct_option_index: 12