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Unformatted text preview: incorrect in part (c) will be a 0.
Exception: If part (a) includes an excellent explanation of a detailed
randomization, a student can get a 1 even if parts (b) and (c) are incorrect. Copyright © 2000 College Entrance Examination Board and Educational Testing Service. All rights reserved.
AP is a registered trademark of the College Entrance Examination Board. AP® Statistics 2000 ─ Scoring Guidelines
Question 6
Solution
a. Large sample confidence interval for a population proportion. Assumptions: large
sample. Here,
ˆ
np = 20 ≥ 5 (or 10) ˆ
n(1 − p) = 380 ≥ 5 (or 10) or
ˆ
p±3 ˆ
ˆ
p(1 − p)
n is in the interval (0,1) ˆ
p ± 1.96 .05 ± 1.96 ˆ
ˆ
p(1 − p)
n
(.05)(.95)
400 .05 ± .02146 (.02854, .07146)
Calculator solution: (.02864, .07136), but still need to name the interval used and check
assumptions.
Interpretation: Based on this sample, we can be 95% confident that the proportion of
married couples for which the wife is taller than her husband is between .028 and .071. Copyright © 2000 College Entrance Examination Board and Educational Testing Service. All rights reserved.
AP is a registered trademark of the College Entrance Examination Board. AP® Statistics 2000 ─ Scoring Guidelines
Question 6 continued
Part (a) is
Essentially correct if (1) identifies the correct procedure either by name
or by formula and checks to make sure sample size is
large enough
(2) has correct computations
(3) gives a correct interpretation in context. Partially correct if correctly does two of the three things required for an
essentially correct response. Notes:
1. In checking assumptions, p, phat, and pi are all acceptable symbols for the sample
proportion.
2. Stating the assumptions is NOT the same as checking the assumptions.
3. A common incorrect response refers to the proportion of times, in repeated sampling,
that a future sample proportion would be contained in “this” interval. This should be read as
an incorrect interpretation.
b. Let M be the height of...
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This note was uploaded on 09/06/2013 for the course MATH AP Statist taught by Professor Mosby during the Spring '13 term at Silverton High School, Silverton.
 Spring '13
 Mosby
 Statistics, AP Statistics

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