hw.prop.CI.Hypo.pVal.STS.KEY

Suppose the population proportion of passengers who

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Unformatted text preview: on board. Suppose the population proportion of passengers who carry on their bags is 0.70 . We intend to take a sample of 25. What is the question being asked of passengers? KEY: are you checking your bag? What is the symbol for the population proportion? KEY: p What is the symbol for the sample proportion? KEY: ^ p Show working in deciding whether it is OK to use the Normal distribution as an estimate. KEY: OK to use Z if np>5 and n(1-p)>5: 25(0.7)=17.5 > 5, 25(0.3)=7.5 > 5 so OK to use Z Compute the probability that the sample proportion will be greater than 0.55 . When you use a formula, show the raw formula with symbols (no numbers) first. Draw a graph and label everything. ^ p-p p(1- p) n 0.55 - 0.70 -0.15 0.55 - 0.70 z= = = 0.09 = Z = -1.67 0.09 0.70(0.30) 25 Area for Z=-1.67 is 0.4525 ^ P(p>0.55) = 0.4525 + 0.5000 = 0.9425 ^ KEY: P(p>0.55): Z = 6. The population proportion of airline passengers checking baggage is unknown. A sample of 25 showed that 16 intended to check their baggage. We'll construct a 95% confidence interval. 6a. This is a CI for what (symbol)? KEY: p p(1 - p) 6b. Write out the standard deviation (in symbols) we would prefer to use: KEY: n 6c. Show working in deciding whether it is OK to use the Normal distribution as an estimate. KEY: We do NOT have p, but must use ^ instead , and ^ = 16/25 = 0.64 p p ^>5 and n(1-p)>5: 25(0.64)=16 > 5, 25(0.36)=9 > 5 so OK to use Z ^ OK to use Z if np ^ (1 - ^) p p 6d. Write out the standard deviation (in symbols) that we must use KEY: n 6e. Construct the 95% confidence interval. First show f...
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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.

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