AP Statistics / Mr. Hansen
2/21/2003

Name: _________________________

Happy Quiz on Chapter 9

1.

Suppose that the true proportion of registered voters in Springfield (pop. 3500) who support Mayor Quimby is 42.5%. In an SRS of 200 registered voters in Springfield, what is the probability that more than 80 support Quimby? Do this 3 ways:

 

 

(a)

Using a binomial approach for the count of 80;

 

 

 

 

 

 

 

 

 

 

 

 

(b)

Using a normal-approximation approach for the sample proportion of .4;

 

 

 

 

 

 

 

 

 

 

 

 

(c)

Using a normal-approximation approach for the count of 80.

 

 

 

 

 

 

 

 

 

 

 

 

2.

Justify why parts (b) or (c) constitute a valid approach.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.

STA students’ heights follow N(70, 2.5) (in inches). Find the probability that in an SRS of 30 students, the mean height exceeds 6 feet.