Study Guide for Test over Scatter Plots and Linear Models

​Remember to find the line of best fit- draw your line exactly through the middle of the data and try to hit at least two data points (dots)!

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​Scatterplots!

Multiple Choice

Given the scatterplot, which of the following would be the line of best fit?

Letter a was incorrect because it was not in the middle of the data​

​While letter b hit some data points, it still was not in the middle of the data

​Wrong answers

​Same number of data points above the line as below- or close

​Line needs to hit a couple of data points

​Qualifications

​The correct answer is C

Some text here about the topic of discussion

​Finding the slope of a scatterplot!

1. Pick two data points on your line

2. Find the change in y over the change in x.​

Multiple Choice

Using the scatterplot, find the slope. Remember, two points have been marked for you with sunshines!

• 10/2

• 3/20

• 20/3

• 5

​The answer is 20/3- remember set up your table

y 40 20​ Change y 20

x 3 0​ Change x 3 so slope is 20/3

Multiple Choice

Next, find the y-intercept (b)

Remember, this is where your graph crosses the y-axis

• 20

• 2

• 10

• 3

​The y-intercept is a (0,20) so b=20. Remember where x is 20 that is our y-intercept. We also know our slope is 20/3. Now we are ready to write our equation in y=mx + b form.

Fill in the Blanks

​Did you get get y=20/3x + 20? Is so, you are correct! Good Job!

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Multiple Choice

If the y axis is distance, and the x axis is time, what is the distance after 5 minutes? Use your equation, y=50/3 x + 20. Remember x is time.

• 40 feet

• 45 feet

• 50 feet

• 53 feet

​The answer is 53 because we used the equation. Just replace x with 5 and solve

y= (20/3)(5) + 20

y= ​100/3 + 20 which is approximately 53!

Multiple Choice

How long will it take you to go 70 feet- this time use the graph and not the equation.

• Between 7 and 8 minutes

• 7 minutes

• 8 minutes

• any of these could work

​When using your scatterplot, refer to your line of best fit. That is why the answer will be between 7 and 8 minutes- like 7.5 or 7.6 minutes.

Multiple Choice

Write an equation in standard form for the following:

Sandwiches cost $4 and pizzas cost $5. I spent T dollars.

• T= 5s + 4p

• T= 4s + 5p

• T= 4s + 5

• T= 5s + 4

​The answer is 4s + 5p = T or is could also be

T= 4s +5p. Standard form is ax +​ by=c so both variables are on one side of the equation.

​The answer is T= .50c + 1.25d. The c is for the candy bar and the d is for the drink.

​Your answer may have varied a little and still been correct, but I have the answer as

.01p + .05n= $1.42​

​Graph the equation 3x -6y=12

1. Find x intercept 3x = 12, x= 4

2. Find y intercept -6y= 12, y= -2

3. Connect the intercepts on the graph

   with a line.

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• Remember y is zero at the x-intercept

• x is zero at the y- intercept​

Multiple Choice

What is the x and y intercept of the following equation?

-2x + 5y = -10

• x= -5

  y= -2

• x= 5

  y= -2

• x= -2

  y= 5

• x= 2

  y= -5

​-2x + 5y = -10

The answer is b because....

x intercept -2x = -14 and -14/-2 is positive 5

y intercept 7y = -14 and -14/7 is -2​

Draw

Now that you know the x intercept is 5 and the y intercept is -2, you try to locate the intercepts and draw the graph

​So the correct answer- drawn in is after you identify the x and y intercepts on your graph, draw a "straight" :( line.

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Graph of equation

-2x + 5y = -10​

Draw

Graph x + 2y = 2. Remember to first identify the x and y intercepts.

​x + 2y = 2

x intercept is x =2

y intercept is 2y=2 so y = 1​

Multiple Choice

How many people were surveyed?

• 20

• 30

• 40

• 50

​Remember the TOTAL is in the bottom

right hand corner- 50!

Open Ended

What does the 12 mean?

​12 means there are 12 girls who like French.

Open Ended

What does 30 mean?

​There was a total of 30 girls interviewed!

Multiple Choice

What is the relative frequency of picking a boy who likes Spanish?

• 10/20

• 1/2

• 1/10

• 4/5

​The answer is 1/2 because 10 out of 20 boys like Spanish but don't forget.... reduce your answer!

​You answer should be 3/5. This is reduced from 15/25.