# Line of Best Fit Calculator

The Line of Best Fit Calculator is a free online tool that displays scatter plots for the given data points. STUDYQUERIES’ online line of best-fit calculator tool makes the calculation faster and displays the line graph in a matter of seconds.

## How to Use the Line of Best Fit Calculator?

To use the line of best-fit calculator, follow these steps:

Step 1: Enter the data points separated by a comma in the respective input field.
Step 2: Now click the button “Calculate Line of Best Fit” to get the line graph.
Step 3: Finally, the straight line that represents the best data on the scatter plot will be displayed in the new window.

## What is the Line Of Best Fit?

There is a line through a scatter plot of data points that best expresses the relationship between them. Either by hand calculations or by using regression analysis software, statisticians arrive at the geometric equation for the line using the least-squares method. From a simple linear regression analysis of two or more independent variables, a straight line will result. When multiple related variables are included in a regression, a curved line can appear.

### Basics of Line Of Best Fit

Among the most important outputs of regression analysis is the line of best fit. R is a measure of the relationship between one or more independent variables and a resulting dependent variable. Professionals in many fields use regression, from science and public service to financial analysis.

During a regression analysis, a statistician collects a collection of data points, each including a set of dependent and independent variables. The dependent variable could be the stock price of a company, and the independent variables could be the Standard and Poor’s 500 indexes and the national unemployment rate, assuming that the stock is not part of the S&P 500. For the past 20 years, each of these three data sets could be sampled.

On a chart, these data points would appear as scatter plots, a group of points that may or may not be arranged along any lines. In case a linear pattern is apparent, it may be possible to sketch a line of best fit that minimizes the distance between those points and the line. In the absence of an organizing axis, regression analysis can generate a line using least-squares. By minimizing the squared distance between each point and the line of best fit, this method builds the line.

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A statistician inputs these three results for the past 20 years into a regression software program to determine the formula for this line. In order to calculate the causal relationship between the S&P 500, the unemployment rate, and the stock price of the company, the software produces a linear formula. This formula corresponds to the line of best fit. Analysts and traders can use it to forecast the stock price of a firm based on two independent variables.

### The Line of Best Fit Equation and Its Components

A regression with two independent variables such as the example discussed above will produce a formula with this basic structure:

$$y= c + b_1(x_1) + b_2(x_2)$$

Y is the dependent variable, c is a constant, b1 is the first regression coefficient, and x1 is the first independent variable. b2 is the second coefficient, and x2 is the second independent variable. From the above example, the stock price would be y, the S&P 500 would be x1, and the unemployment rate would be x2. With each additional unit of the independent variable, the coefficient of that variable represents the degree of change in y.

An S&P 500 increase by one will result in a corresponding increase in share price equal to the coefficient. A higher unemployment rate will also result in a higher share price. The coefficient of a simple regression with one independent variable is the slope of the line of best fit. Any regression with two independent variables has a slope that is a mixture of the two coefficients. Constant c is the y-intercept of the line of best fit.

NOTE:

1. The Line of Best Fit is used to express a relationship in a scatter plot of different data points.
2. It is an output of regression analysis and can be used as a prediction tool for indicators and price movements.

### Line of Best Fit (Least Square Method)

The best fit line is a straight line that approximates the given set of data as closely as possible.

It is used to examine the nature of the relationship between two variables. (We are only considering the two-dimensional case.)

With an eyeball method, a line of best fit can be roughly determined by drawing a straight line on a scatter plot so that the number of points above and below the line is equal (and the line passes through as many points as possible).

The least squares method is a more accurate way to determine the line of best fit.

Use the following steps to find the equation of the line of best fit for a set of ordered pairs $$(x_1,y_1),(x_2,y_2),…(x_n,y_n)$$

Step 1: Calculate the mean of the x -values and the mean of the y -values.

$$\bar{X}=\frac{\sum_{i=1}^{n}X_i}{n}$$

$$\bar{Y}=\frac{\sum_{i=1}^{n}Y_i}{n}$$

Step 2: The following formula gives the slope of the line of best fit:

$$m=\sum_{i=1}^{n}(X_i-\bar{X})(Y_i-\bar{Y})$$

$$m=\sum_{i=1}^{n}(X_i-\bar{X})^2$$

Step 3: Compute the y-intercept of the line by using the formula:

$$b=\bar{Y}-m\bar{X}$$

Step 4: Use the slope m and the y-intercept b to form the equation of the line.

Example:

Use the least square method to determine the equation of the line of best fit for the data. Then plot the line.

Solution: Plot the points on a coordinate plane.

Calculate the means of the x -values and the y -values.

$$\bar{X}=\frac{\sum_{i=1}^{10}X_i}{10}=\frac{8+2+11+6+5+4+12+9+6+1}{10}=6.4$$

$$\bar{Y}=\frac{\sum_{i=1}^{10}Y_i}{10}=\frac{3+10+3+6+8+12+1+4+9+14}{10}=7$$

$$Now\ calculate\ X_i-\bar{X} , Y_i-\bar{Y} , (X_i-\bar{X})(Y_i-\bar{Y}) , and\ (X_i-\bar{X})^2\ for\ each\ i$$

$$m=\sum_{i=1}^{10}(X_i-\bar{X})(Y_i-\bar{Y})=\sum_{i=1}^{10}(X_i-\bar{X})^2=\frac{-131}{118.4}\approx-1.1$$

Calculate the y -intercept.

Use the formula to compute the y-intercept.

$$b=\bar{Y}-m\bar{X}=7-(-1.1\times6.4)\approx14.0$$

Use the slope and y-intercept to form the equation of the line of best fit.

The slope of the line is −1.1 and the y-intercept is 14.0.

Therefore, the equation is $$y=−1.1x+14.0$$

Draw the line on the scatter plot.

### Correlation Coefficients

The correlation coefficient measures the “goodness of fit” of the best fit line (least-squares line). The correlation coefficient indicates the measure of linear association between two variables, as well as whether the correlation is positive or negative. It ranges between -1 and 1, inclusive.

A correlation coefficient, designated by r, is a number in the range -1 < r < 1, which indicates how well a regression equation truly represents the data being examined.

• If r is close to 1 (or -1), the model is considered a “good fit”.
• If r is close to 0, the model is “not a good fit”.
• If r = ±1, the model is a “perfect fit” with all data points lying on the line.
• If r = 0, there is no linear relationship between the two variables.

A correlation greater than 0.8 is generally described as strong, whereas a correlation less than 0.5 is generally described as weak. These values can vary based upon the “type” of data being examined. A study utilizing scientific data may require a stronger correlation than a study using social science data.

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## FAQs

How do you find the line of best fit?

An eyeball method can be used to determine a line of best fit by drawing a straight line on a scatter plot so that the number of points above and below the line is equal (and the line passes through as many points as possible).

What is the line of best fit also known as?

The line of best fit also called a trendline, is the line for which the sum of the squares of the residual errors between individual data values and the line is at its minimum, which is just a fancy way of saying it’s the straightest line that fits your data.

How do you find the line of best fit on Excel?

A dialog box will appear when you right-click on any of the data points. “Add Trendline”; this is what Excel calls a “best-fit line”. An options window appears where you can choose the type of Trend/Regression.

Does the line of best fit have to start at 0?

There is no need to go through the origin for the line of best fit. The line of best fit reveals the trend, but it is only approximate, so any readings derived from it are estimates.

Why is the regression line known as the line of best fit?

Because it is the line that fits best when drawn through the points, the regression line is sometimes called the “line of best fit.” The regression line minimizes the difference between actual and predicted scores.