Math Problem Statement

What's not true about a correlation coefficient r?

Solution

The question is asking about the correlation coefficient rr and which statement is not true.

Here is an analysis of each option:

  1. 1r1-1 \leq r \leq 1

    • This is true. The correlation coefficient rr always lies between 1-1 and 11.
  2. The closer rr is to ±1, the more closely the scattered points line up.

    • This is also true. When rr is close to +1+1 or 1-1, the data points lie closer to a straight line.
  3. r>0r > 0 when scatter plot shows a rising trend.

    • This is true. A positive rr indicates a positive correlation, meaning a rising trend in the data.
  4. rr is the slope of the best-fit line.

    • This is not true. The correlation coefficient rr measures the strength and direction of the linear relationship between variables, but it is not the slope of the line of best fit. The slope is a separate value.
  5. r<0r < 0 when scatter plot shows a falling trend.

    • This is true. A negative rr indicates a negative correlation, meaning a downward trend.

Correct Answer:

"rr is the slope of the best-fit line."

Would you like me to explain correlation coefficients further or break down other concepts related to this question?


Related Questions:

  1. What is the significance of a correlation coefficient r=0r = 0?
  2. How does rr differ from the slope of a regression line?
  3. How is the correlation coefficient rr calculated mathematically?
  4. Can the correlation coefficient indicate causation? Why or why not?
  5. What does a perfect positive correlation (r=1r = 1) look like on a scatter plot?

Tip: Remember, the correlation coefficient rr describes association, not the actual slope of a line.

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Math Problem Analysis

Mathematical Concepts

Statistics
Correlation Coefficient
Scatter Plots

Formulas

-1 ≤ r ≤ 1

Theorems

Correlation Coefficient Properties

Suitable Grade Level

High School, Grades 10-12