How to test if reaction times differ?

Dear all,

I am going to do an eye movement experiment in which I want to manipulate a
certain variable. However, I want to make sure that the manipulation works
before doing the whole experiment. Therefore, I want to determine whether
eye movements to the left have become significantly slower than eye
movements to the right.

To do this I will have 25 eye movement to the left & 25 to the right -->
Test significance --> if it is not significant --> increase
manipulation ---> 25 to the right and left, etc. --> Until the difference is
significant.

Assumption: Nothing will happen with the eye movements to the right
(reaction time and variance will be the same).

My question is how can I test this?

Kind regards,

Martijn


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