### sMAPE

How to calculate sMAPE Subtract the actual value from the absolute forcast Square the result Find the square root of the previous result (step #2) sMAPE = Square Root ( F – A)^2

### Why is 2-tail p-value twice the 1-tail p-value?

Why is the two-tail p-value always twice the one-tail p-value in a t-test? In the t-test output below, notice that the two-tail p-value is 0.66852 while the one-tail p-value is 0.33426. The two-tail p-value is twice the one-tail p-value. Why is this true? The two-tail p-value is defined as P > |t|. That is, the

### Correlation: Introduction to Relationships

In the last lesson, you learned about the Two-way Chi-square Test for Independence. Using it, you can determine if two categorical variables are independent. If two variables are not independent, they are related. Knowing something about one variable can tell you something about the other variable. In this lesson, you will explore further this idea

### Correlation and Chi-square Tests for Independence

The word “correlate” has several meanings, e.g. “If two or more facts, numbers, etc. correlate or are correlated, there is a relationship between them” (Cambridge Dictionary, n.d.) And “to show that a close connection exists between (two or more things)” (Merriam-Webster, 2019) Also, “to show that two things are connected.” (Macmillan, n.d.) In statistics, we often