# 6 5: The Method of Least Squares Mathematics LibreTexts

Least squares is a method of finding the best line to approximate a set of data. These properties underpin the use of the method of least squares for all types of data fitting, even when the assumptions are not strictly valid. For example, it is easy to show that the arithmetic mean of a set of measurements of a quantity is the least-squares estimator of the value of that quantity. If the conditions of the Gauss–Markov theorem apply, the arithmetic mean is optimal, whatever the distribution of errors of the measurements might be. The are some cool physics at play, involving the relationship between force and the energy needed to pull a spring a given distance.

The method of least squares grew out of the fields of astronomy and geodesy, as scientists and mathematicians sought to provide solutions to the challenges of navigating the Earth’s oceans during the Age of Discovery. The accurate description of the behavior of celestial bodies was the key to enabling ships to sail in open seas, where sailors could no longer rely on land sightings for navigation. This section covers common examples of problems involving least squares and their step-by-step solutions.

- Our fitted regression line enables us to predict the response, Y, for a given value of X.
- Next, find the difference between the actual value and the predicted value for each line.
- The index returns are then designated as the independent variable, and the stock returns are the dependent variable.

Some of the data points are further from the mean line, so these springs are stretched more than others. The springs that are stretched the furthest exert the greatest force on the line. To emphasize that the nature of the functions \(g_i\) really is irrelevant, consider the following example. To emphasize that the nature of the functions g

i

really is irrelevant, consider the following example. Although the inventor of the least squares method is up for debate, the German mathematician Carl Friedrich Gauss claims to have invented the theory in 1795.

The English mathematician Isaac Newton asserted in the Principia (1687) that Earth has an oblate (grapefruit) shape due to its spin—causing the equatorial diameter to exceed the polar diameter by about 1 part in 230. In 1718 the director of the Paris Observatory, Jacques Cassini, asserted on the basis of his own measurements that Earth has a prolate (lemon) shape. This formula is particularly useful in the sciences, as matrices with orthogonal columns often arise in nature. Here’s a hypothetical example to show how the least square method works. Let’s assume that an analyst wishes to test the relationship between a company’s stock returns, and the returns of the index for which the stock is a component.

## The Sum of the Squared Errors SSE

Each point of data represents the relationship between a known independent variable and an unknown dependent variable. This method is commonly used by statisticians and traders who want to identify trading opportunities and trends. The Least Squares Method is used to derive a generalized linear equation between two variables, one of which is independent and the other dependent on the former. The value of the independent variable is represented as the x-coordinate and that of the dependent variable is represented as the y-coordinate in a 2D cartesian coordinate system.

This data might not be useful in making interpretations or predicting the values of the dependent variable for the independent variable where it is initially unknown. So, we try to get an equation of a line that fits best to the given data points with the help of the Least Square Method. The least squares method seeks to find a line that best approximates a set of data.

This method of fitting equations which approximates the curves to given raw data is the least squares. Dependent variables are illustrated on the vertical y-axis, while independent variables are illustrated on the horizontal x-axis in regression analysis. These designations form the equation for the line of best fit, which is determined from the least squares method.

## Q3: What are the assumptions in the least Square Method?

In this example, the analyst seeks to test the dependence of the stock returns on the index returns. Investors and analysts can use the least square method by analyzing past performance and making predictions about future trends in the economy and stock markets. The two basic categories of least-square problems are ordinary or linear least squares and nonlinear least squares.

The index returns are then designated as the independent variable, and the stock returns are the dependent variable. The line of best fit provides the analyst with coefficients explaining reduce inventory loss the level of dependence. Least square method is the process of fitting a curve according to the given data. It is one of the methods used to determine the trend line for the given data.

## Is Least Squares the Same as Linear Regression?

Therefore, adding these together will give a better idea of the accuracy of the line of best fit. It’s a powerful formula and if you build any project using it I would love to see it. Regardless, predicting the future is a fun concept even if, in reality, the most we can hope to predict is an approximation based on past data points. It will be important for the next step when we have to apply the formula. We get all of the elements we will use shortly and add an event on the “Add” button. That event will grab the current values and update our table visually.

## Least Squares – Explanation and Examples

A mathematical procedure for finding the best-fitting curve to a given set of points by minimizing the sum of the squares of the offsets (“the residuals”) of

the points from the curve. The sum of the squares of the offsets is used instead

of the offset absolute values because this allows the residuals to be treated as

a continuous differentiable quantity. However, because squares of the offsets are

used, outlying points can have a disproportionate https://intuit-payroll.org/ effect on the fit, a property which

may or may not be desirable depending on the problem at hand. Where the true error variance σ2 is replaced by an estimate, the reduced chi-squared statistic, based on the minimized value of the residual sum of squares (objective function), S. The denominator, n − m, is the statistical degrees of freedom; see effective degrees of freedom for generalizations.[12] C is the covariance matrix.

The least-square method states that the curve that best fits a given set of observations, is said to be a curve having a minimum sum of the squared residuals (or deviations or errors) from the given data points. Let us assume that the given points of data are (x1, y1), (x2, y2), (x3, y3), …, (xn, yn) in which all x’s are independent variables, while all y’s are dependent ones. Also, suppose that f(x) is the fitting curve and d represents error or deviation from each given point.

This line can be then used to make further interpretations about the data and to predict the unknown values. The Least Squares Method provides accurate results only if the scatter data is evenly distributed and does not contain outliers. Another thing you might note is that the formula for the slope \(b\) is just fine providing you have statistical software to make the calculations. But, what would you do if you were stranded on a desert island, and were in need of finding the least squares regression line for the relationship between the depth of the tide and the time of day?

Then, we try to represent all the marked points as a straight line or a linear equation. The equation of such a line is obtained with the help of the least squares method. This is done to get the value of the dependent variable for an independent variable for which the value was initially unknown. This helps us to fill in the missing points in a data table or forecast the data.

It turns out that minimizing the overall energy in the springs is equivalent to fitting a regression line using the method of least squares. In order to find the best-fit line, we try to solve the above equations in the unknowns \(M\) and \(B\). As the three points do not actually lie on a line, there is no actual solution, so instead we compute a least-squares solution. In order to find the best-fit line, we try to solve the above equations in the unknowns M

and B

.