The F Distribution and the F-Ratio · Exercise 3

Groups of men from three different areas of the country are to be tested for mean weight. The entries in are the weights for the different groups.
$$\begin{array}{ccc}\text{Group 1}& \text{Group 2}& \text{Group 3}\\ \text{216}& \text{202}& \text{170}\\ \text{198}& \text{213}& \text{165}\\ \text{240}& \text{284}& \text{182}\\ \text{187}& \text{228}& \text{197}\\ \text{176}& \text{210}& \text{201}\end{array}$$

What is the df for the numerator?

OpenStax, Introductory Statistics 2e · §13.2 The F Distribution and the F-Ratio · Exercise 3