Is this sentence grammatical?

[ououou]

Dear Teachers,

I would like to write a sentence which means my subjects' preference for something is around 50%. Is the following senstence correct?

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Their preference for A is about chance level.
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Thank you.

[Tdol]

It doesn't make much sense to me- if I had heard it without the explanation, I wouldn't have got the idea. Can you have a preference of 50%? Surely, to prefer, it has to be over 50%? Or do you mean that half prefer it?

[ououou]

Dear tdol,

Thanks very much for your reply.
In fact, I was reporting the results from an experiment with 10 questions, in which 20 subjects were asked to tell which answer (of two choices) they preferred. Basically, the result showed that these subjects averagely preferred one of the answers at around 50% of the time (=no preferece). However, in another experiment with the similar design, they preferred one of the answers at 80% of the time (=preference). My purpose of writing that sentence is to make my writing more changeable to express the meaning of "no preferece". I remembered I read some expression like "chance level" but couldn't find it for imitation at this moment. So if you know how to write that sentense correctly, I would appreciate it very much!

Once again, thanks for your time!