AP Statistics / Mr. Hansen	Name: _______________________________________
2/28/2007

Test on Chapter 9 and Beginning of Chapter 10

• Calculator is OK throughout.
• If a blank is provided, give the short answer that fits best. If several lines of blanks are provided, write an essay of the approximate length indicated. Shorter is acceptable if you cover everything that needs to be said.
• If a gap is provided, provide adequate justification/explanation, and circle your answer.
• Point values are shown in parentheses in the left margin.

1. (15 pts.)	Explain why an understanding of sampling distributions is essential to the practice of inferential statistics (i.e., confidence intervals and tests of statistical significance). ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________
2.(a) (10)	A P-value, as you know, is a conditional probability. Modify the definition below, which is wrong, in order to make a correct version.
	“The P-value of a test is the probability that chance alone is the only force at work, given that H0 is true, when we obtain a test statistic as extreme as or more extreme than the one seen.
(b) (5)	Is it possible to compute the probability originally printed in part (a)? ____ Why or why not?
	______________________________________________________________________ ______________________________________________________________________
3. (10)	In a significance test, we are looking to see whether there is sufficient evidence to _________ the _________ hypothesis. If there is not sufficient evidence, is the null hypothesis considered to have been proved? ____ Why or why not? ________________________________________
4. (9)	A P-value of _____ (fill in a number) or _________ (fill in “less” or “greater”) is often considered to be the threshold of significance. Is there anything special about this value, or is it simply a common convention with no special importance? _______________________________________
5. (6)	A significance test addresses only the issue of whether a result is plausible or implausible given ______ alone. A significance test has nothing to do with whether a result is of any _____________ significance.
6. (18)	List the 7 steps in a significance test, along with a word or a few words for each. One has been filled in for you as an example:
	___ ___________________________ ___ ___________________________ ___ ___________________________ (S) (optional) Sketch of the sampling distribution, assuming H0 is true ___ ___________________________ ___ ___________________________ ___ ___________________________
7.	I wish to determine if Smokey is biased in favor of selecting Michael Raffaniello. His probability of being selected should be 1/15, since there are 15 STAtistics students, but in 200 trials, Smokey picks Michael Raffaniello 37 times.
(a) (5)	Compute a 95% confidence interval for the true probability that Smokey selects Michael Raffaniello (in interval format). Show your work.
(b) (5)	Give the answer to part (a) in “estimate ± m.o.e.” format.
(c) (14)	Perform a significance test (all 7 steps) for the question posed in the first sentence of the problem. Continue on a separate sheet if necessary.
(d) (3)	Is your approach in (c) one-tailed or two-tailed?