Answers:
- Line of best fit: b = 0.40n+30
- The average cost of each extra call is 40 cents.
- Pete pays 43.60 dollars in a month when he makes 34 calls.
Please read the disclaimer below.
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Step-by-step explanation:
Disclaimer: The issue is that without the coordinate values, it's impossible to determine the regression line. It's not clear where some (or most) of the red points are located. Often that's why a table is needed. I would ask your teacher for clarification.
With that said, I'll still give it a shot.
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Part 1
The blue regression line appears to go through the two points (0,30) and (50,50). Let's find the slope through this line
m = (y2-y1)/(x2-x1)
m = (50-30)/(50-0)
m = 20/50
m = 0.40
The y intercept is b = 30 since the blue line appears to cross the y axis at this location.
So y = mx+b turns into y = 0.40x+30
Replace x with n and replace y with b
We go from y = 0.40x+30 to b = 0.40n+30 which is the regression line.
Again this is all based on the assumptions that the blue line goes through (0,30) and (50,50).
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Part 2
Assuming we have the correct regression equation, we can immediately see that each extra call costs $0.40 which is the same as 40 cents. So it's 40 cents per call. This is the slope value, which is the rate of change. Each time n goes up by 1, b goes up by 0.40
Because the regression line estimates the actual observed values, we won't always land on a red point. But the goal is to get as close as possible.
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Part 3
Again assuming we have the correct regression equation, we plug in n = 34 and evaluate to determine the bill
b = 0.40*n + 30
b = 0.40*34 + 30
b = 43.60
Pete would pay $43.60 if he made 34 calls.