Relationship between them: They solve the same application problem and can be used to express the direction and tightness of the relationship between two numerical variables. Both correlation coefficients have no unit, and the value range is 1 to 1. In the calculation, the rank correlation coefficient is obtained by using rank as product moment correlation.
The difference between the two: different data requirements. The product moment correlation requires and obeys the binary normal distribution, and the rank correlation can be arbitrary distribution. Because of the different requirements for data, they belong to parametric statistical method and nonparametric statistical method respectively, so the efficiency of product moment correlation is higher than rank correlation under the condition of satisfying binary normal distribution. These two hypothesis testing methods are different.
A straight line consists of countless points, and the points move into a line. A straight line is a part of a surface and then constitutes a body. There is no end point, extending to both ends indefinitely, and the length cannot be measured. A straight line is an axisymmetric figure. It has countless symmetry axes, all of which are straight lines perpendicular to it (there are countless). There is only one straight line between two non-overlapping points on the plane, that is, two non-overlapping points determine a straight line.
On the sphere, countless similar straight lines can be made after two points. The most basic element of geometry. In the axiomatic system of Euclidean geometry established by D Hilbert, points, lines and surfaces belong to basic concepts, which are defined by their relationships and five groups of axioms.
Mathematically, Euclidean geometry is a common geometry in plane and three-dimensional space, based on the assumptions of points, lines and surfaces. Mathematicians also use this term to represent high-dimensional geometry with similar properties. The five axioms of Euclid geometry are: any two points can be connected by a straight line; Any line segment can be infinitely extended into a straight line.
Given any line segment, you can make a circle with an endpoint as the center and a line segment as the radius; All right angles are congruent; If both straight lines intersect with the third line, and the sum of internal angles on the same side is less than the sum of two right angles, then the two straight lines must intersect at that side.