Math Problem Statement

The table below gives the number of hours spent unsupervised each day as well as the overall grade averages for seven randomly selected middle school students. Using this data, consider the equation of the regression line, yˆ=b0+b1xy^=b0+b1x, for predicting the overall grade average for a middle school student based on the number of hours spent unsupervised each day. Keep in mind, the correlation coefficient may or may not be statistically significant for the data given. Remember, in practice, it would not be appropriate to use the regression line to make a prediction if the correlation coefficient is not statistically significant.

Hours Unsupervised

00

0.50.5

1.51.5

2.52.5

44

4.54.5

66

Overall Grades

8888

7979

7676

7272

6565

6363

6262

Solution

To find the equation of the regression line, y^=b0+b1x\hat{y} = b_0 + b_1x, follow these steps:


Steps:

  1. Identify the regression line formula:

    • y^=b0+b1x\hat{y} = b_0 + b_1x, where: b1=nxyxynx2(x)2b_1 = \frac{n\sum{xy} - \sum{x}\sum{y}}{n\sum{x^2} - (\sum{x})^2} b0=yb1xnb_0 = \frac{\sum{y} - b_1\sum{x}}{n}
  2. Extract data:

    • xx: Hours unsupervised
    • yy: Overall grades
  3. Compute necessary sums:

    • x,y,x2,y2,xy\sum{x}, \sum{y}, \sum{x^2}, \sum{y^2}, \sum{xy}
  4. Calculate b1b_1 and b0b_0.


Data:

[ x = [0, 0.5, 1.5, 2.5, 4, 4.5, 6], \quad y = [88, 79, 76, 72, 65, 63, 62] ]

Let's compute the required values.x = np.array([0, 0.5, 1.5, 2.5, 4, 4.5, 6]) # Hours unsupervised y = np.array([88, 79, 76, 72, 65, 63, 62]) # Overall grades

Number of data points

n = len(x)

Calculate sums

sum_x = np.sum(x) sum_y = np.sum(y) sum_x2 = np.sum(x2) sum_y2 = np.sum(y2) sum_xy = np.sum(x * y)

Calculate slope (b1)

b1 = (n * sum_xy - sum_x * sum_y) / (n * sum_x2 - sum_x**2)

Calculate intercept (b0)

b0 = (sum_y - b1 * sum_x) / n

b0, b-importing required library after code state reset import numpy as np

Data

x = np.array([0, 0.5, 1.5, 2.5, 4, 4.5, 6]) # Hours unsupervised y = np.array([88, 79, 76, 72, 65, 63, 62]) # Overall grades

Number of data points

n = len(x)

Calculate sums

sum_x = np.sum(x) sum_y = np.sum(y) sum_x2 = np.sum(x2) sum_y2 = np.sum(y2) sum_xy = np.sum(x * y)

Calculate slope (b1)

b1 = (n * sum_xy - sum_x * sum_y) / (n * sum_x2 - sum_x**2)

Calculate intercept (b0)

b0 = (sum_y - b1 * sum_x) / n

b0, b### Equation of the Regression Line: The regression line for predicting overall grade average based on the number of hours spent unsupervised is:

y^=83.3694.136x\hat{y} = 83.369 - 4.136x


Interpretation:

  1. Slope (b1=4.136b_1 = -4.136):
    • For every additional hour spent unsupervised, the predicted grade decreases by approximately 4.136 points.
  2. Intercept (b0=83.369b_0 = 83.369):
    • If a student spends 0 hours unsupervised, the predicted grade is approximately 83.369.

Would you like to analyze the significance of the correlation coefficient or make predictions using this regression line?


Follow-up Questions:

  1. What is the predicted grade for a student spending 3 hours unsupervised?
  2. Is the correlation coefficient for this data statistically significant?
  3. Can this model be used reliably for predictions?
  4. How does the steep negative slope reflect on the data's trend?
  5. Are there any outliers that could significantly influence the regression line?

Tip:

Always verify the statistical significance of the correlation coefficient before interpreting or using the regression line for predictions.

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Math Problem Analysis

Mathematical Concepts

Statistics
Linear Regression
Correlation

Formulas

Regression Line: yˆ = b0 + b1x
Slope: b1 = (n∑xy - ∑x∑y) / (n∑x^2 - (∑x)^2)
Intercept: b0 = (∑y - b1∑x) / n

Theorems

Least Squares Regression Line

Suitable Grade Level

Grades 9-12