Math Problem Statement

A computer, while calculating the correlation coefficient between two variables x and y, gave the following information: n = 25, Σx = 125, Σy = 100, Σx² = 650, Σy² = 460, Σxy = 508. It was discovered that the operator had copied down two pairs of observations incorrectly: Incorrect values: (x = 6, y = 14) and (x = 8, y = 6); Correct values: (x = 8, y = 12) and (x = 6, y = 8). Obtain the correct value of the correlation coefficient between x and y.

Solution

The problem involves calculating the correct value of the correlation coefficient after identifying and correcting errors in the provided data.

Given Data:

  • n=25n = 25
  • Σx=125\Sigma x = 125
  • Σy=100\Sigma y = 100
  • Σx2=650\Sigma x^2 = 650
  • Σy2=460\Sigma y^2 = 460
  • Σxy=508\Sigma xy = 508

However, the operator incorrectly recorded two pairs of observations:

  • Incorrect: (x1=6,y1=14),(x2=8,y2=6)(x_1 = 6, y_1 = 14), (x_2 = 8, y_2 = 6)
  • Correct: (x1=8,y1=12),(x2=6,y2=8)(x_1 = 8, y_1 = 12), (x_2 = 6, y_2 = 8)

To calculate the correct correlation coefficient:

  1. Adjust the sums: We need to first adjust the incorrect values and update the following sums:
    • Σx\Sigma x
    • Σy\Sigma y
    • Σx2\Sigma x^2
    • Σy2\Sigma y^2
    • Σxy\Sigma xy

Step-by-Step Corrections:

Let’s calculate the differences caused by the incorrect values and apply the corrections.


I will now proceed with calculations to adjust the sums and find the correct correlation coefficient.The correct value of the correlation coefficient between xx and yy after adjusting for the errors is approximately r=0.667r = 0.667.

Would you like more details on any step, or do you have any further questions?

Here are five related questions that can expand your understanding:

  1. How is the correlation coefficient interpreted in statistical analysis?
  2. What does a correlation coefficient of 0.667 indicate about the relationship between xx and yy?
  3. How can outliers affect the value of the correlation coefficient?
  4. What are the assumptions for using the Pearson correlation coefficient?
  5. How does the correlation coefficient relate to the concept of covariance?

Tip: When computing correlation coefficients, it's essential to verify the data entry, as errors can significantly affect the result.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Correlation coefficient
Statistics
Data correction
Summation adjustment

Formulas

r = (nΣxy - ΣxΣy) / sqrt[(nΣx² - (Σx)²)(nΣy² - (Σy)²)]
Correction formulas for Σx, Σy, Σx², Σy², and Σxy after data correction

Theorems

Pearson correlation coefficient

Suitable Grade Level

Undergraduate Statistics