Frogs, part II. Based on concerns raised by his preliminary research, the biologist in Exercise 28 decides to collect and examine 150 frogs.

a) Assuming the frequency of the trait is still 1 in 8, determine the mean and standard deviation of the number of frogs with the trait he should expect to find in his sample.

b) Verify that he can use a Normal model to approximate the distribution of the number of frogs with the trait.

c) He found the trait in 22 of his frogs. Do you think this proves that the trait has become more common?

Explain.