Hello everyone!

A TV producer claims that 40 percent of parents watch his TV show. By the time when the show was transmitted, 100 parents were called on the phone, and it was found that 30 of them were watching the show. With $\displaystyle \alpha = 0.05$, was the producer right?

I'm confused with the standard deviation here! There isn't and I don't know how to find it!

THanks