Question

Given the data points, (x, y) of a linear function: (2, 11), (4, 10), (6, 9), (12, 6), what is the function? What is the slope? What is the intercept?

Answer 1

Answer:

The function is $y~=~12 ~-~ 0.5 \cdot x$.

The slope is $m=-0.5$.

The y-intercept is $b=12$.

Step-by-step explanation:

Our aim is to calculate the values m (slope) and b (y-intercept) in the equation of a line :

$y=mx+b$

We have the following data:

$\begin{array}{c|cccc}x&2&4&6&12\\y&11&10&9&6\end{array}$

To find the line of best fit for the points given, you must:

Step 1: Find $X\cdot Y$and $X\cdot X$ as it was done in the table below.

Step 2: Find the sum of every column:

$\sum{X} = 24 ~,~ \sum{Y} = 36 ~,~ \sum{X \cdot Y} = 188 ~,~ \sum{X^2} = 200$

Step 3: Use the following equations to find b and m:

$\begin{aligned} b &= \frac{\sum{Y} \cdot \sum{X^2} - \sum{X} \cdot \sum{XY} }{n \cdot \sum{X^2} - \left(\sum{X}\right)^2} = \frac{ 36 \cdot 200 - 24 \cdot 188}{ 4 \cdot 200 - 24^2} \approx 12 \\ \\m &= \frac{ n \cdot \sum{XY} - \sum{X} \cdot \sum{Y}}{n \cdot \sum{X^2} - \left(\sum{X}\right)^2} = \frac{ 4 \cdot 188 - 24 \cdot 36 }{ 4 \cdot 200 - \left( 24 \right)^2} \approx -0.5\end{aligned}$

Step 4: Assemble the equation of a line

$\begin{aligned} y~&=~b ~+~ m \cdot x \\y~&=~12 ~-~ 0.5 \cdot x\end{aligned}$

The graph of the regression line is: