Question

The graph shows the relationship between the number of months different students practiced boxing and the number of matches they won: Part A: What is the approximate y-intercept of the line of best fit and what does it represent? (5 points)

Part B: Write the equation for the line of best fit in the slope-intercept form and use it to predict the number of matches that could be won after 13 months of practice. Show your work and include the points used to calculate the slope. (5 points)

Answer 1

@jim_thompson5910

Answer 2

Have you learned how to do linear regression?

Answer 3

no

Answer 4

hmm, then how do they want you do to this? Let me think

Answer 5

Does it give you the coordinates of the points?

Answer 6

no you have them on the graph though

Answer 7

yeah but it's hard to tell where exactly each point is located

Answer 8

you can just do the whole numbers they dont have to be halves or decimals

Answer 9

This is an unfair problem because not enough information is given. And they expect accurate answers I'm assuming

Answer 10

thats what i was thinking but can you try your best and explain it to me

Answer 11

ok so I'm not 100% sure but let's say we focused on these two points

the red and blue points you see in the attached image

Answer 12

okay

Answer 13

Look at the coordinates that I list. Make sure you understand how I got those coordinates.

Answer 14

how did you get these coordinates

Answer 15

here's how I got (9,18). The red point

Answer 16

agreed? or no?

Answer 17

oh why couldnt you use 3,9

Answer 18

I'm focusing on points that lie on the line drawn

Answer 19

oh okay

Answer 20

i understand

Answer 21

do you see how I got (8,16.5) ?

Answer 22

yes

Answer 23

if (8, 16.5) and (9,18) are on the line, then what is the slope of this line?


Use the slope formula


\[\Large m = \frac{y_2 - y_1}{x_2 - x_1}\]

Answer 24

umm

Answer 25

subtract the y values
18 - 16.5 = ???

Answer 26

1.5

Answer 27

subtract the x values
9-8 = ???

Answer 28

wherw did you get 18

Answer 29

where*

Answer 30

from (9,18)

Answer 31

ohh nevermind

Answer 32

okay im catching on

Answer 33

subtract the x values
9-8 = ???

Answer 34

the x would be 1

Answer 35

subtract the y values
18 - 16.5 = 1.5

subtract the x values
9-8 = 1


Divide the y difference over the x difference

1.5/1 = 1.5

So the slope of this line is 1.5

Answer 36

so m = 1.5

Answer 37

so it would be y=1.5x+3

Answer 38

now use y = mx+b

m = 1.5
x = 9
y = 18

and solve for b

Answer 39

`so it would be y=1.5x+3`
no

Answer 40

y=1.5x+18

Answer 41

y = mx+b

18 = 1.5*9 + b

solve for b

Answer 42

we don't do it like that in my class

Answer 43

you use point slope form?

Answer 44

we do Y=slope {m}+y intercept {b}

Answer 45

and the x just stays x

Answer 46

so basically what I wrote out but with words added in

Answer 47

but you put the first y into 18

Answer 48

when you should do the last y

Answer 49

(9,18) is on the graph
so x = 9 and y = 18

Answer 50

i thought the y intercept would be 3

Answer 51

y = mx+b

18 = m*9 + b ... replace x with 9 and replace y with 18

18 = 1.5*9 + b ... replace m with 1.5

Answer 52

`i thought the y intercept would be 3`
it's slightly bigger

Answer 53

so 3.5

Answer 54

solve for b to find out

Answer 55

18 = 1.5*9 + b

18 = 13.5 + b

b = ???

Answer 56

this is getting confusing

Answer 57

13.5 plus _______ = 18

what must go in the blank?

Answer 58

4.5

Answer 59

yep, that's the y intercept

Answer 60

so the equation of the regression line is y = 1.5x + 4.5

Answer 61

oh okay let me write that down hold on

Answer 62

Keep in mind that we're basing all of this off the assumption this line goes through (8,16.5) and (9,18). Hopefully this assumption is true but it's impossible to say based on just the graph alone.

Answer 63

thank you but what can we predict how many games there going to win after 13 months

Answer 64

x = number of months

plug in x = 13 to find the value of y

Answer 65

oh so 18

Answer 66

or 17.5

Answer 67

no 18 is incorrect

Answer 68

sorry i meant 17.5

Answer 69

y = 1.5*x + 4.5
y = 1.5*13 + 4.5 ... replace x with 13
y = 19.5 + 4.5
y = 24

Answer 70

oh

Answer 71

So if you practice for 13 months, then it's predicted you'll win about 24 matches

Answer 72

okay im going to write this down and we have one more question im going to close this when im done writing it down and tag you