Answer
The requirement of equal population variances for each treatment is verified.
Work Step by Step
In MINITAB 18, enter the data according to the table below.
Select Stat -> Basic Statistics -> Display Descriptive Statistics
In Variables enter 28-day strength (psi) (C3). In By variables enter Slump Mixture (C1 C2).
Click in Statistics. Select Standard deviation. Click Ok.
Click Ok.
Lowest standard deviation: 319.7
Highest standard deviation: 167.7
But, $319\lt2\times167.7$
