Question

There is a statistical difference between groups as the p-value is less than 5%. Do I need to perform a post-hoc test? Why or why not?

SUMMARY
Groups	Count	Sum	Average	Variance
Column 1	22	1420318	64559.90909	83671674.28
Column 2	15	1295223	86348.2	72184280.89
Column 3	13	2145812	165062.4615	10933748061
ANOVA
Source of Variation	SS	df	MS	F	P-value	F crit
Between Groups	85073726515	2	42536863258	14.92269054	9.60024E-06	3.19505628
Within Groups	1.33973E+11	47	2850482167
Total	2.19046E+11	49

Answer 1

The p-value corresponding to Between Groups is less than 5% which indicates that there is a significant statistical difference between the mean values of the three given groups of the question.
We need to perform a post-hoc test to determine which of those among the three groups have a significantly different mean value compared to the others. We select pairs from these three groups and we try to find which pair differs significantly with respect to mean values.