As a? follow-up to a report on gas? consumption, a consumer group conducted a st
ID: 2428493 • Letter: A
Question
As a? follow-up to a report on gas? consumption, a consumer group conducted a study of SUV owners to estimate the mean mileage for their vehicles. A simple random sample of 88 SUV owners was? selected, and the owners were asked to report their highway mileage. The results that were summarized from the sample data were x over x equals=18.5 mpg and sequals=5.5 mpg. Based on these sample? data, compute and interpret a 90?% confidence interval estimate for the mean highway mileage for SUVs. The
90?% confidence interval is _____ to _______mpg
Explanation / Answer
ANSWER:
MEAN = 18.5 MPG
STD = 5.5 MPG
N = 88
Z VALUE AT 90% CONFIDENCE = 1.645
CI = MEAN +- Z VALUE * ( STD / N) ^ 1/2
CI = 18.5 +- 1.645 * ( 5.5 / 88) ^ 1/2
CI = 18.5 +- 1.645 * (.0625) ^ 1/2
CI = 18.5 +- 1.645 * 0.25
CI = 18.5 +- 0.41125
CI = (18.911 , 18.088)
SO 90% CONFIDENCE INTERVAL RANGES FROM 18.088 MPG TO 18.911 MPG
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