Math Problem Statement

The Cotton Mill is an upscale chain of women’s clothing stores, located primarily in the southwest United States. As a result of recent success, The Cotton Mill’s top management is planning to expand by locating new stores in other regions of the country. The director of planning has been asked to study the relationship between yearly sales and the store size. As part of the study, the director selects a sample of 25 stores and determines the size of the store in square feet and the sales for last year. The sample data follow. The use of statistical software is suggested.

Store Size (thousands of square feet) Sales (millions $) Store Size (thousands of square feet) Sales (millions $) 3.7 9.18 0.4 0.55 2.0 4.58 4.2 7.56 5.0 8.22 3.1 2.23 0.7 1.45 2.6 4.49 2.6 6.51 5.2 9.90 2.9 2.82 3.3 8.93 5.2 10.45 3.2 7.60 5.9 9.94 4.9 3.71 3.0 4.43 5.5 5.47 2.4 4.75 2.9 8.22 2.4 7.30 2.2 7.17 0.5 3.33 2.3 4.35 5.0 6.76 Determine the correlation coefficient and the coefficient of determination.

Note: Round your answers to 3 decimal places.

Solution

pandas as pd import numpy as np from scipy.stats import pearsonr

Data input

data = { "Store_Size": [3.7, 2.0, 5.0, 0.7, 2.6, 2.6, 2.9, 5.2, 5.2, 5.9, 3.0, 5.5, 2.4, 2.9, 2.4, 2.2, 0.5, 4.2, 3.3, 3.2, 0.4, 5.0, 2.3], "Sales": [9.18, 4.58, 8.22, 1.45, 4.49, 6.51, 2.82, 9.90, 10.45, 9.94, 4.43, 5.47, 4.75, 8.22, 7.30, 7.17, 3.33, 7.56, 8.93, 7.60, 0.55, 6.76, 4.35] }

Create a dataframe

df = pd.DataFrame(data)

Calculate correlation coefficient

correlation_coefficient, _ = pearsonr(df["Store_Size"], df["Sales"])

Calculate coefficient of determination (R^2)

coefficient_of_determination = correlation_coefficient ** 2

correlation_coefficient, coefficient_of_determinationThe correlation coefficient is r=0.755r = 0.755 (rounded to three decimal places), indicating a strong positive linear relationship between store size and sales.

The coefficient of determination is R2=0.569R^2 = 0.569 (rounded to three decimal places), meaning approximately 56.9% of the variation in sales can be explained by the store size.

Would you like further analysis or have any specific questions?

Here are five related questions for exploration:

  1. Would you like to see a scatter plot of the data with a trendline?
  2. Should we perform a linear regression to model the relationship?
  3. Do you want to calculate confidence intervals for these coefficients?
  4. Would you like to analyze outliers in this dataset?
  5. Should we test the statistical significance of the correlation?

Tip: Always consider visualizing your data to understand relationships better before relying solely on numerical measures.

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Math Problem Analysis

Mathematical Concepts

Statistics
Correlation
Linear Relationships

Formulas

Correlation coefficient formula: r = Σ((x - x̄)(y - ȳ)) / √(Σ(x - x̄)²Σ(y - ȳ)²)
Coefficient of determination formula: R² = r²

Theorems

Pearson Correlation Coefficient

Suitable Grade Level

Undergraduate/Advanced High School