Hypothesis testing using binomial?

[edmondo93]

A company developed synthetic coffee and claim that coffee drinkers could not distinguish it from the real product. A number of coffee drinkers challanged the company's claim, saying that the synthetic coffee tasted synthetic. In a test, carried out by an independent consumer protection body, 20 people were given a mug of coffee. Ten had the synthetic brand and ten the natural, but they were not told which they had been given.

Out of the ten given the synthetic brand, eight said it was synthetic and two said it was natural. Use this information to test the coffee drinkers' claim, at the 5% significance level.
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I am not sure what the null and alternative hypothesis is in this question, but my guess is

H0 : p = 1/2

H1 : p>1/2

this is as far as I can get.