• The regression line is the straight line that best represents the relationship between two variables on a scatter diagram.
• It is used to estimate the value of y when the value of x is known.
• The best line is the one that makes the sum of the squared differences between the actual values of y and the values predicted by the line as small as possible.
• This method is called the method of least squares.
• The regression equation of y on x is written as:

ŷ = a + bx

• where b is the slope, meaning the expected change in y when x increases by one unit, and a is the value of y when x = 0.
• Regression differs from correlation.
• Correlation measures the strength and direction of a relationship without treating one variable as the cause of the other.
• Regression assumes that y depends on x, and it gives an equation that can be used for prediction.