# OECD Threatened species data analysis 3 - ANOVA(ANalysis Of VAriance) without lm() and anova()

In this brlog, let's do ANOVA(Analysis of Variance).

We see average Value(percentage of threatened species) are different by SUBJECT. BIRD has the highest Value and PLANT has the lowest.
But this difference is statistically significant?

Let's check it in R. We can use lm() function. Use anova() to see the results. p-value is 0.0303, so it is significant at 5% significant level.

Now, let's do ANOVA without lm() and summary() function.

1. calculate overall average.  2. calculate average by SUBJECT 3. calculate variance by SUBJECT We get 10990.3 4. Calculate overall sum of squares 5. Calculate SSE = SST - SSA We got 779.9 6. calculate degree of freedom for SUBJECT We get 2. 7. Calculatedegree of freedom for Residuals. We got 102 Now, we got 2, 102, 779.9 and 10990.3.

8. we can calculate Mean Sq.

SUBJECT Mean Sq = 779.9 / 2 = 389.96

Residuals Mean Sq = 10990.3 / 102 = 107.75  9. Calculate F-value. We got 3.6192 10. Calculate p-value Nice! Finally we got 0.0303! That's it.

Next blog is...

If you would like to see the first blog.