X^2 Contingency table

Question

In the French population, the distribution of the variable 'Gender' is known and is as follows: 50% men and 50%women. A research wishes to investigate whether the distribution of the variable "gender" in the population of university students differs from the known distribution in the French population. He draws a SRS of size n=100 from the population of university students and finds the following counts: 30 men and 70 women. Which statement is correct?

1) 0,05 < p < 0,10

2) 0,0025 < p < 0,005

3) 0 < p < 0.0005

I know from my solution book that 3 is correct, but I don't understand why. I'd be thankful for an explanation

Answer 1

Chi-square value = (70-50)^2/50 + (30-50)^2/50 = 16 with 1 degree of freedom. P(chi-square > 16) with 1 DOF is less than 0.0001.