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 Blank

Ok, now that we know b= 20 and m= 20/3, write an equation in y= mx+b form

​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.

Fill in the Blank

Now it is your turn, write an equation in standard form for the following:

The market was selling candy bars for $.50 each and drinks for $1.25. Let T be the total cost.

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

Fill in the Blank

Now try one with money. Remember to use the denominations values in front of your letters. For example .25q would be a quarter. Ok, so write an equation in standard form for the following:

I have pennies and nickels in my wallet that total $1.42.

​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!

Fill in the Blank

Ok, for the final question, of the people who like Spanish, what is the relative frequency of picking a girl? Write as a REDUCED FRACTION!

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