You can easily find the critical F value given the significance level alpha with our . If you want to find the critical F value by using a table with critical F values, instructions are given below.
Finding the critical value $F^*$ given a significance level $\alpha$, using the table with critical $F$ values
Assuming a table giving five upper tail probabilities (denoted $p$ or $\alpha$) per df numerator / df denominator combination
Reject the null hypothesis if the observed $F$ falls in the highest $\alpha$ area of the $F$ distribution. In order to find the critical value $F^*$ that corresponds to this upper tail area: