Math Problem Statement

1. The capital and profit (in thousand peso) of ten businessmen are shown below. Find the correlation coefficient using Pearson r and describe the degree of relationship. 2. The table below shows the monthly income and monthly expenses of seven families in a certain barangay in Makati. Compute for the correlation coefficient using Spearman rho and describe the degree of relationship.

Solution

Let's start by addressing the first problem.

1. Pearson Correlation Coefficient

The formula for Pearson's correlation coefficient (rr) between two variables XX (Capital) and YY (Profit) is:

[ r = \frac{n \sum (XY) - \sum X \sum Y}{\sqrt{[n \sum X^2 - (\sum X)^2][n \sum Y^2 - (\sum Y)^2]}} ]

Where:

  • nn is the number of data points (here, n=10n = 10),
  • XX represents the Capital,
  • YY represents the Profit.

Steps:

  1. Calculate X\sum X, Y\sum Y, XY\sum XY, X2\sum X^2, and Y2\sum Y^2.
  2. Plug the values into the formula to find rr.

Table of values:

BusinessmenCapital (XX)Profit (YY)X×YX \times YX2X^2Y2Y^2
120510040025
250157502500225
3103301009
410030300010000900
51847232416
625922562581
71166612136
81507010500225004900
95315259
1040156001600225

Now, let's compute the sums:

  • X=429\sum X = 429
  • Y=160\sum Y = 160
  • XY=15108\sum XY = 15108
  • X2=37795\sum X^2 = 37795
  • Y2=6426\sum Y^2 = 6426

Substituting into Pearson's formula:

[ r = \frac{10 \times 15108 - 429 \times 160}{\sqrt{[10 \times 37795 - 429^2][10 \times 6426 - 160^2]}} ] [ r = \frac{151080 - 68640}{\sqrt{[377950 - 183041][64260 - 25600]}} ] r=82440194909×386608244086871.20.949r = \frac{82440}{\sqrt{194909 \times 38660}} \approx \frac{82440}{86871.2} \approx 0.949

So, the Pearson correlation coefficient r0.949r \approx 0.949, indicating a strong positive correlation between Capital and Profit.


2. Spearman Rank Correlation Coefficient

For the second problem, we need to compute the Spearman Rank correlation coefficient for Income and Expenses. The formula is:

ρ=16di2n(n21)\rho = 1 - \frac{6 \sum d_i^2}{n(n^2 - 1)}

Where:

  • did_i is the difference between the ranks of the two variables (Income and Expenses),
  • nn is the number of pairs (here, n=7n = 7).

We rank the Income and Expenses, compute the rank differences, and apply the formula.

Would you like me to continue solving this second part in full detail?


5 Related Questions:

  1. How do we interpret the value of a Pearson correlation coefficient?
  2. What are some assumptions behind the use of Pearson's rr?
  3. How does Spearman's correlation differ from Pearson's correlation?
  4. What is the impact of outliers on Pearson correlation?
  5. Can two variables have a high Spearman correlation but a low Pearson correlation?

Tip:

When data contains outliers or is not normally distributed, Spearman's rank correlation is often a better choice than Pearson's correlation.

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Math Problem Analysis

Mathematical Concepts

Correlation
Pearson Correlation Coefficient
Spearman Rank Correlation

Formulas

Pearson's Correlation Coefficient formula: r = [nΣ(XY) - ΣXΣY] / sqrt{[nΣ(X^2) - (ΣX)^2][nΣ(Y^2) - (ΣY)^2]}
Spearman's Rank Correlation formula: ρ = 1 - (6Σd_i^2) / n(n^2 - 1)

Theorems

Pearson's correlation theorem
Spearman's rank correlation theorem

Suitable Grade Level

Grades 11-12