Math Problem Statement

how to find linear correlation coefficient

Solution

To find the linear correlation coefficient (also known as Pearson's correlation coefficient, denoted as r), follow these steps:

Steps to Calculate Linear Correlation Coefficient:

  1. Gather Data:

    • You need two sets of data, let's call them X={x1,x2,...,xn}X = \{x_1, x_2, ..., x_n\} and Y={y1,y2,...,yn}Y = \{y_1, y_2, ..., y_n\}, where nn is the number of data points.
  2. Calculate the Mean of XX and YY:

    • xˉ=1ni=1nxi\bar{x} = \frac{1}{n} \sum_{i=1}^{n} x_i
    • yˉ=1ni=1nyi\bar{y} = \frac{1}{n} \sum_{i=1}^{n} y_i
  3. Calculate the Numerator:

    • Compute the covariance between XX and YY: Cov(X,Y)=i=1n(xixˉ)(yiyˉ)\text{Cov}(X, Y) = \sum_{i=1}^{n} (x_i - \bar{x})(y_i - \bar{y})
  4. Calculate the Denominator:

    • Compute the standard deviation of XX and YY: σx=i=1n(xixˉ)2\sigma_x = \sqrt{\sum_{i=1}^{n} (x_i - \bar{x})^2} σy=i=1n(yiyˉ)2\sigma_y = \sqrt{\sum_{i=1}^{n} (y_i - \bar{y})^2}
  5. Compute the Correlation Coefficient:

    • The Pearson correlation coefficient is given by: r=Cov(X,Y)σxσyr = \frac{\text{Cov}(X, Y)}{\sigma_x \sigma_y} This value will range between 1-1 and 11:
    • r=1r = 1: Perfect positive correlation.
    • r=1r = -1: Perfect negative correlation.
    • r=0r = 0: No linear correlation.

Example:

Suppose you have two sets of dataTo find the linear correlation coefficient (also known as Pearson's correlation coefficient, denoted as r), follow these steps:

Steps to Calculate Linear Correlation Coefficient:

  1. Gather Data:

    • You need two sets of data, let's call them X={x1,x2,...,xn}X = \{x_1, x_2, ..., x_n\} and Y={y1,y2,...,yn}Y = \{y_1, y_2, ..., y_n\}, where nn is the number of data points.
  2. Calculate the Mean of XX and YY:

    • xˉ=1ni=1nxi\bar{x} = \frac{1}{n} \sum_{i=1}^{n} x_i
    • yˉ=1ni=1nyi\bar{y} = \frac{1}{n} \sum_{i=1}^{n} y_i
  3. Calculate the Numerator:

    • Compute the covariance between XX and YY: Cov(X,Y)=i=1n(xixˉ)(yiyˉ)\text{Cov}(X, Y) = \sum_{i=1}^{n} (x_i - \bar{x})(y_i - \bar{y})
  4. Calculate the Denominator:

    • Compute the standard deviation of XX and YY: σx=i=1n(xixˉ)2\sigma_x = \sqrt{\sum_{i=1}^{n} (x_i - \bar{x})^2} σy=i=1n(yiyˉ)2\sigma_y = \sqrt{\sum_{i=1}^{n} (y_i - \bar{y})^2}
  5. Compute the Correlation Coefficient:

    • The Pearson correlation coefficient is given by: r=Cov(X,Y)σxσyr = \frac{\text{Cov}(X, Y)}{\sigma_x \sigma_y} This value will range between 1-1 and 11:
    • r=1r = 1: Perfect positive correlation.
    • r=1r = -1: Perfect negative correlation.
    • r=0r = 0: No linear correlation.

Example:

Suppose you have two sets of

  • X={1,2,3,4,5}X = \{1, 2, 3, 4, 5\}
  • Y={2,4,6,8,10}Y = \{2, 4, 6, 8, 10\}

Follow the steps to calculate rr and it will give you a value of r=1r = 1, indicating a perfect positive correlation.

Would you like a worked-out example or any clarifications?

5 Related Questions:

  1. How does the correlation coefficient differ from covariance?
  2. What does a correlation coefficient of 0.5 indicate?
  3. How do outliers affect the value of the correlation coefficient?
  4. Can you calculate the correlation coefficient for non-linear relationships?
  5. How is the correlation coefficient used in regression analysis?

Tip: A correlation coefficient close to 0 does not always mean no relationship; it could indicate a non-linear relationship.

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Math Problem Analysis

Mathematical Concepts

Statistics
Correlation
Linear Relationships

Formulas

Pearson's correlation coefficient: r = Cov(X, Y) / (σx * σy)
Mean: x̄ = (1/n) Σ xi and ȳ = (1/n) Σ yi
Covariance: Cov(X, Y) = Σ (xi - x̄)(yi - ȳ)
Standard Deviation: σx = sqrt(Σ (xi - x̄)^2), σy = sqrt(Σ (yi - ȳ)^2)

Theorems

Properties of the Pearson Correlation Coefficient

Suitable Grade Level

Grades 10-12