Computing Type 1 Error Rate for Coin Test

[EvLer]

How would I compute the type 1 error rate of the following test:

accept that coin is fair if in 30 tosses the coin gives between 11 and 19 heads (inclusive), reject otherwise.

I guess my Ho is 11/30<p<19/30
and H1: p < 11/30 or p > 19/30

so type I prob = P(p < 11/30) + P(p > 19/30) both under Ho.
Is this correct?

thanks

 

[TripleS]

it should be right, i think