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Unformatted text preview: ormula with symbols only. Show work. Use 3 decimal
places for the standard deviation.
^ (1 - ^)
p(1 - p)
KEY: ^ ± Z*
but must use ^ ± Z*
0.64 ± 1.96*⎜
6f. State the interpretation of the CI. KEY: We are 95% Confident that the unknown population
proportion p is in the interval [0.45, 0.83]
6g. Suppose our null hypothesis is Ho: p ≥ 0.55 . Compute the p-value. Show all work including the raw
formula with symbols (no numbers). No credit unless proper subscripts are used everywhere. Use 3
decimal places for the standard deviation.
^ sample - p
0.64 - 0.55
Area for Z = 0.91 is 0.3186.
p-value is on the same side as alpha – it has the same
"tail" as alpha.
Thus, the p-value = 0.5000 + 0.3186 = 0.8186 6h.
7a. What is the decision based on this p-value? KEY: can't reject, since the p-value is so large
We'll test at α = 0.01 whether the population proportion of airline passengers checking baggage is at least
0.55 . A sample of 25 passengers showed 9 checked their baggage.
Determine whether it is OK to use the Normal distribution for this problem.
KEY: OK to use Z if np>5 and n(1-p)>5: 25(0.55)=13.75 > 5, 25(0.45)=11.25 > 5 so OK to use Z 7b. Hypothesis testing using the regular method: Show all work including the raw formula with symbols (no
numbers). No credit unless proper subscripts are used everywhere. Use 3 decimal places for the standard
deviation. Draw a graph and fill it out completely.
State Hypotheses KEY: Ho p ≥ 0.55 H1...
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This note was uploaded on 01/27/2013 for the course STAT 385 taught by Professor Szatrowski during the Spring '08 term at Rutgers.
- Spring '08