Astatistician controls by establishing the risk he or she is willing to take in terms of rejecting a true null hypothesis.
a) alpha
b) beta
c) mean
d) standard deviation

a) Alpha

Step-by-step explanation:

The correct option is alpha because alpha known as type I error is the probability of reject the null hypothesis when null  hypothesis is true. If we take alpha 5%, it means that we are taking 5 out of 100 chance of rejecting the null hypothesis when it is true.

So, statistician controls alpha by establishing the risk of rejecting a null hypothesis when its true.

The correct option is D) 17,202 feet.

Step-by-step explanation:

Consider the provided information.

The required diagram is shown below:

It is given that the distance from the observer (O) to the bird (B) is 21,000 ft.

Let x is the distance between Nest and Bird.

As we know

The value of

Hence, the distance between bird (B) from its nest (N) is 17,202 feet.

Thus, the correct option is D) 17,202 feet.