The starting material used in this experiment is actually a mixture of cis and trans isomers. The question is, does that have any effect on the effectiveness of the dehydration, which we know to be an E1 reaction?
The answer is no, for both cis and trans isomers will first have to form the same flat carbocation, which then undergoes the elimination step.
The carbocation then undergoes elimination to form the product, regardless of whether the initial alcohol was cis or trans.
If this was an E2 reaction, then the structure of the starting material could make a difference because of the anticoplanar requirement for E2 reactions