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: ^
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. ^
0.55 - 0.70 -0.15
0.55 - 0.70
= 0.09 = Z = -1.67
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:
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
^>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 - ^)
6d. Write out the standard deviation (in symbols) that we must use KEY:
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.
- Spring '08