8th Grade Math : Data

Study concepts, example questions & explanations for 8th Grade Math

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Example Questions

Example Question #8 : 8th Grade Math

The scatter plot provided displays a group of students' test scores versus the number of missing assignments the students have. Based on plot, select the best answer that describes the direction of the points. 

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Possible Answers:

A positive, nonlinear association

A negative, linear association

A negative, non linear association 

A positive, linear association

Correct answer:

A negative, linear association

Explanation:

The data points in the scatter plot move up the y-axis as the x-axis decreases; thus the data points show a negative association. Also, the data points do not curve, or go up and down, but gradually decreased; thus the scatter plot shows a linear association. We could even draw a "best fit" line:

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Example Question #9 : 8th Grade Math

A teacher at a high school conducted a survey of seniors and found that \displaystyle 81 students owned a laptop and \displaystyle 54 of those students also had a car. There were \displaystyle 22 students that did not have a laptop, but owned a car. Last, they found that \displaystyle 17 students did not own a laptop nor a car. Given this information, how many students had a laptop, but did not own a car? 

Possible Answers:

\displaystyle 81

\displaystyle 17

\displaystyle 54

\displaystyle 27

Correct answer:

\displaystyle 27

Explanation:

To help answer this question, we can construct a two-way table and fill in our known quantities from the question.

The columns of the table will represent the students who have a laptop or do not have a laptop and the rows will contain the students who have a car or do not have a car. The first bit of information that we were given from the question was that \displaystyle 81 students had a laptop; therefore, \displaystyle 81 needs to go in the "laptop" column as the row total. Next, we were told that of those students, \displaystyle 54 owned a car; therefore, we need to put \displaystyle 54 in the "laptop" column and in the "car" row. Then, we were told that \displaystyle 22 students do not own a laptop, but own a car, so we need to put \displaystyle 22 in the "no laptop" column and the "car" row. Finally, we were told that \displaystyle 17 students do not have a laptop or a car, so \displaystyle 17 needs to go in the "no laptop" column and "no car" row. If done correctly, you should create a table similar to the following: 

Screen shot 2016 03 25 at 10.07.17 am

Our question asked how many students have a laptop, but do not own have a car. We can take the total number of students that own a lap top, \displaystyle 81, and subtract the number of students who have a car, 

\displaystyle \frac{\begin{array}[b]{r}81\\ -\ 54\end{array}}{ \ \ \ \space 27}

This means that \displaystyle 27 students who have a laptop, don't have a car. 

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