Buzz words in job requirement - ANOVA

One of the popular buzz word is ANOVA, which is acronym of analysis of variance.

1. What type of problem can be solved by ANOVA?
There are several samples, which could be generated by different methods. ANOVA can test if means of these sample are different. In the context of marketing, several campaigns are run among different countries and impact of the campaigns (revenue maybe) is recorded. ANOVA can test if impact of campaigns differs among different countries.

2. ANOVA v.s. t test of means by two groups
If there are only two groups, t test can be used instead of ANOVA for simplicity.

3. The idea of ANOVA
If means of the sample groups are assumed to identical, then error of each observation is due to two reasons. One is the error within sample, the other is between samples.

when SS_A is relative larger than SS_withinwithin, we can say that means of different samples are different.

4. Formula of one-way ANOVA
Formula is always boring. You can find it here.