Math Problem Statement

Given the data (x: [1, 2, 3, 4], y: [2, 3, 7, 8]), find the correlation coefficient, describe the relation between x and y, find the regression line equation, and explain the meaning of the coefficients.

Solution

Let's analyze and solve the given problems based on the table provided. The data shows values for xx and yy:

xx1234
yy2378

(a) Find the correlation coefficient rr

The formula for the correlation coefficient rr is:

r=nxyxy(nx2(x)2)(ny2(y)2)r = \frac{n\sum{xy} - \sum{x}\sum{y}}{\sqrt{\left(n\sum{x^2} - (\sum{x})^2\right)\left(n\sum{y^2} - (\sum{y})^2\right)}}

Where:

  • nn is the number of data points (in this case 4).
  • x,y\sum{x}, \sum{y} are the sums of xx and yy values.
  • xy\sum{xy} is the sum of the products of xx and yy values.
  • x2,y2\sum{x^2}, \sum{y^2} are the sums of the squares of xx and yy values.

I will calculate the correlation coefficient next.

(b) Describe the relation between xx and yy

This asks for a general description of the relationship, which can be inferred from the correlation coefficient and how the values change together.

(c) Find the equation y=ax+by = ax + b of the regression line for yy on xx

To find the regression line, we use the least squares method: a=nxyxynx2(x)2a = \frac{n\sum{xy} - \sum{x}\sum{y}}{n\sum{x^2} - (\sum{x})^2} b=yx2xxynx2(x)2b = \frac{\sum{y}\sum{x^2} - \sum{x}\sum{xy}}{n\sum{x^2} - (\sum{x})^2} where aa is the slope, and bb is the intercept.

(d) Describe what the coefficient aa represents

The coefficient aa represents the slope of the regression line. It indicates the rate of change of yy with respect to xx.

(e) Describe what the constant bb represents

The constant bb represents the y-intercept of the regression line. It shows the value of yy when x=0x = 0.

I'll calculate these values now.Here are the results:

(a) Correlation coefficient rr

The correlation coefficient r=0.965r = 0.965 (approximately). This indicates a strong positive correlation between xx and yy.

(b) Describe the relation between xx and yy

There is a strong positive linear relationship between xx and yy, as the correlation coefficient is close to 1. This suggests that as xx increases, yy also increases significantly.

(c) Equation of the regression line

The regression equation is:

y=2.2x0.5y = 2.2x - 0.5

(d) What does the coefficient aa represent?

The coefficient a=2.2a = 2.2 represents the slope of the line. For every unit increase in xx, yy increases by 2.2 units.

(e) What does the constant bb represent?

The constant b=0.5b = -0.5 is the y-intercept. It indicates that when x=0x = 0, yy would be 0.5-0.5.

Would you like further clarification or details on any part of this?

Here are 5 related questions:

  1. How do we interpret the correlation coefficient in different ranges?
  2. What if the correlation coefficient rr was negative?
  3. Can we use this regression line to predict values of yy for xx values outside the given range?
  4. How does the strength of correlation affect the reliability of predictions?
  5. What would happen if there were more data points added to the set?

Tip: A strong correlation does not imply causation, even though it indicates a relationship between variables.

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Math Problem Analysis

Mathematical Concepts

Correlation coefficient
Linear regression
Slope and intercept interpretation

Formulas

Correlation coefficient formula: r = (nΣxy - ΣxΣy) / sqrt((nΣx² - (Σx)²)(nΣy² - (Σy)²))
Regression line equation: y = ax + b
Slope formula: a = (nΣxy - ΣxΣy) / (nΣx² - (Σx)²)
Intercept formula: b = (ΣyΣx² - ΣxΣxy) / (nΣx² - (Σx)²)

Theorems

Least Squares Method

Suitable Grade Level

Grades 10-12