In ANOVA, what does F=1 mean?

F=1 means that the variance of means (factor) =variance of the error.

The F distribution is the distribution of the ratio of two estimates
of variance. It is used to compute probability values in the analysis
of variance. The F distribution has two parameters: degrees of freedom
numerator (dfn) and degrees of freedom denominator (dfd). The dfn is
the number of degrees of freedom that the estimate of variance used in
the numerator is based on. The dfd is the number of degrees of freedom
that the estimate used in the denominator is based on. The dfd is
often called the degrees of freedom error or dfe. In the simplest case
of a one-factor between-subjects ANOVA,

see http://davidmlane.com/hyperstat/A107688.html


 
but in fact F is used to compare between the calculation and the
tables to see if your hypotesis should be accepted or rejected.