standard_description: Develop a probability model and use it to find probabilities of events. Compare probabilities from a model to observed frequencies; if the agreement is not good, explain possible sources of the discrepancy.
problem_activity: Problem 1
Akilah is running for seventh-grade class president. There are 100 students in the seventh grade at her school. To better understand her chances of winning, Akilah asks a random sample of 20 seventh graders if they plan to vote for her. In her sample, 12 out of the 20 students said they planned to vote for her. Akilah asks several friends to also ask a random sample of 20 students. Together, they combine their results to get a better understanding of her chances of winning. After winning the election, Akilah finds out that 55 out of the 100 seventh graders at her school voted for her.
Using the situation above, define and describe the following terms:
a.   sample
b.   population
c.   sample proportion
d.   population proportion
e.   sample distribution
Problem 2
All two hundred middle school students at Roosevelt Middle School responded to several survey questions, and the results were combined in a table which your teacher will share with you.
The first column represents a unique student ID number for each student. The last column represents students’ responses to the question “Which of the following superpowers would you most like to have: invisibility, super strength, telepathy, fly, or freeze time?”
The class wants to determine the proportion of Roosevelt Middle School students who choose freeze time as their superpower.
a.   In your group, use the random number table to collect a random sample of 20 student responses to the superpower question. Record your data in a table.
b.   Determine the sample proportion for your sample.
c.   Will the other groups in your class have the same sample proportion as you? Explain your reasoning.
d.   Collect the sample proportions from the class and present the distribution in a dot plot. According to the dot plot, what is a good estimation for the population proportion? What is a good estimation for the number of students who chose freeze time as their superpower?
Problem 3
This diagram shows some trees in a tree farm. The circles show old trees and the triangles show young trees. Tom wants to know how many trees there are of each type, but he says it would take too long to count them all one by one. (Note, there are 50 columns and 50 rows in the diagram.)
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a.   What method could he use to estimate the number of trees of each type? Explain your method fully.
b.   On the
Counting Trees Worksheet
, use your method to estimate the number of old trees and young trees.


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