Math Problem Statement

A company is using a system of payment by results. The union claims that this seriously discriminates against the workers. there is a fairly steep learning curve which workers follow with the apparent outcome that more experienced workers can perform the task in about half of the time taken by the new employee. You have been asked to find out if there is any basis for this claim. To do this, you have observed ten workers on the shop floor, timing how long it takes them to produce an item. It was then possible for you to match these times with the length of worker’s experience. The results obtained are shown below:- Month’s experience 2 5 3 8 5 9 12 16 1 6 Time taken 27 26 30 20 22 20 16 15 30 19 Required: (a) Find the regression line of time taken on month’s experience (b) Compute the coefficient of correlation and coefficient of determination and interpret

Solution

To address the questions:

(a) Regression Line of Time Taken on Month’s Experience

The regression line is given by the formula: y=a+bxy = a + bx Where:

  • yy: Dependent variable (time taken)
  • xx: Independent variable (month's experience)
  • bb: Slope of the regression line b=(xy)nxˉyˉ(x2)nxˉ2b = \frac{\sum(xy) - n\bar{x}\bar{y}}{\sum(x^2) - n\bar{x}^2}
  • aa: Intercept of the regression line a=yˉbxˉa = \bar{y} - b\bar{x}

(b) Coefficient of Correlation (rr) and Coefficient of Determination (r2r^2)

The formula for the correlation coefficient (rr) is: [ r = \frac{\sum(xy) - n\bar{x}\bar{y}}{\sqrt{[\sum(x^2) - n\bar{x}^2][\sum(y^2) - n\bar{y}^2]}} ] The coefficient of determination (r2r^2) measures the proportion of variance in the dependent variable explained by the independent variable.

Let’s compute these using the given data:

Month’s Experience (xx)Time Taken (yy)
227
526
330
820
522
920
1216
1615
130
619

I will calculate the required values.import pandas as pd import numpy as np

Data

data = { "Months_Experience": [2, 5, 3, 8, 5, 9, 12, 16, 1, 6], "Time_Taken": [27, 26, 30, 20, 22, 20, 16, 15, 30, 19] } df = pd.DataFrame(data)

Calculations

x = df["Months_Experience"] y = df["Time_Taken"] n = len(df)

Summations

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)

Means

mean_x = np.mean(x) mean_y = np.mean(y)

Regression coefficients

b = (sum_xy - n * mean_x * mean_y) / (sum_x2 - n * mean_x**2) a = mean_y - b * mean_x

Correlation coefficient (r)

r = (sum_xy - n * mean_x * mean_y) / np.sqrt((sum_x2 - n * mean_x2) * (sum_y2 - n * mean_y2))

Coefficient of determination (r^2)

r_squared = r**2

Results

regression_line = f"y = {a:.2f} + {b:.2f}x" regression_line, r, r_squared('y = 29.59 + -1.06x', -0.904288815081655, 0.8177382610817837)('y = 29.59 + -1.06x', -0.904288815081655, 0.8177382610817837)success### Results:

(a) Regression Line:

The regression line of time taken (yy) on months of experience (xx) is: y=29.591.06xy = 29.59 - 1.06x

(b) Coefficients:

  • Correlation Coefficient (rr): 0.904-0.904
    This indicates a strong negative correlation between time taken and months of experience; as experience increases, time taken decreases significantly.

  • Coefficient of Determination (r2r^2): 0.8180.818
    Approximately 81.8%81.8\% of the variance in the time taken is explained by the worker's months of experience.


Would you like a detailed step-by-step breakdown of the calculations? Let me know if you have questions or need further clarification.

Related Questions:

  1. How does a steep learning curve affect workers' output over time?
  2. Can this regression model predict performance for new employees with zero experience?
  3. What are some ways to mitigate discrimination in a results-based pay system?
  4. Would a nonlinear model better fit this data, given the learning curve?
  5. How can the company use this data to improve the payment system?

Tip:

Always analyze the residuals of your regression to verify if the linear model is appropriate for your data.

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Math Problem Analysis

Mathematical Concepts

Linear Regression
Correlation
Statistics

Formulas

y = a + bx
b = (Σxy - n * x̄ * ȳ) / (Σx² - n * x̄²)
a = ȳ - b * x̄
r = (Σxy - n * x̄ * ȳ) / √[(Σx² - n * x̄²) * (Σy² - n * ȳ²)]

Theorems

Least Squares Method
Correlation and Regression Theorem

Suitable Grade Level

Grades 11-12