How to Show a Relationship Between Two Variables in an Excel Graph

Understanding Correlation

• Correlation measures how strongly two variables are connected. It’s represented by a coefficient called the correlation coefficient.
• If the correlation coefficient is 0, the variables are not correlated (no relationship). A graph of zero correlation appears as a straight line.

• When the correlation coefficient is between -1 and +1, the variables are related. Negative values indicate negative correlation.

• Positive values indicate positive correlation.

Dataset Overview

• Let’s work with a dataset containing information about the height and weight of employees.
• We’ll plot height (x-axis) against weight (y-axis) to explore their relationship.

Step 1 – Creating a Scatter Plot

• Select the range containing height and weight data (e.g., C4:D13).

• Go to the Insert tab and choose the Scatter icon. Select the scatter plot type.

• The scatter plot graph will appear on your sheet.

Step 2 – Customizing the Chart

• To make the graph more understandable:
  • Change the chart title and axis titles.
  • Adjust any other formatting as needed.

Read More: How to Find Correlation Coefficient in Excel Scatter Plot

Step 3 – Adding a Trendline

• Click on the scatter plot chart. A plus (+) icon will appear.
• Click the plus icon to see options and check Trendline.

• A linear trendline will appear on the graph.
• The positive slope of the trendline suggests positive correlation.

Step 4 – Displaying R-Squared Value

• Double-click the trendline to open the Format Trendline settings.
• Check Display R-squared value on chart.

• The R-squared value will now appear on the chart.

Step 5 – Showing the Trendline Equation

• In the same Format Trendline settings, check Display Equation on chart.

• The equation of the linear trendline will be visible.

Step 6 – Calculating the Correlation Coefficient R

• We already have the R-squared value (e.g., 0.6618).
• To find the correlation coefficient, R, use the SQRT function:
  • Select a cell (e.g., D5) and enter the formula:

• • Press Enter to get the result (e.g., 0.8135).
• This value indicates a positive correlation between height and weight.

Read More: How to Calculate Spearman Correlation in Excel

Step 7 – Checking the Correlation Coefficient

• To verify the result from the graph, we’ll calculate the correlation coefficient using the CORREL function.
• Select cell D16 (or any other empty cell where you’d like to display the result).
• Enter the following formula:

• Press Enter to see the result.
• You can see both values of the correlation coefficient are the same.

• Understanding the CORREL Function:
  • The CORREL function calculates the correlation coefficient between two data series (X-variable and Y-variable).
  • In the formula, C5:C13 represents the height data (X-variable), and D5:D13 represents the weight data (Y-variable).

Final Decision

• If both values of the correlation coefficient match, it confirms the accuracy of the graph’s trendline.
• Based on the positive slope of the trendline, we can conclude that the two variables have a positive correlation.
• Additionally, the strong positive correlation (indicated by the value of R) means that if one variable increases, the other also tends to increase.

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Related Articles

• How to Find Spearman Rank Correlation Coefficient in Excel
• How to Calculate Pearson Correlation Coefficient in Excel
• How to Find Coefficient of Determination in Excel
• How to Calculate Intraclass Correlation Coefficient in Excel
• How to Calculate P Value for Spearman Correlation in Excel

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