The F statistic for one-way ANOVA and its P-value depend both on the group means (black dots) and on the spread of the observations within each group (colored squares).
You can move the group means by dragging the black dots with the mouse. You can increase or decrease the spread within the groups by dragging the pooled standard deviation s along the scale at the top. Watch the P-value change on the scale at the bottom. The value of the F statistic appears in red under the P-value scale.