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Statistics STA 2023 Finals Review (Tests 4, 5, 6) Questions and Complete Solutions Graded A+
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Statistics STA 2023 Finals Review (Tests 4, 5, 6) Questions and Complete Solutions Graded A+
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Statistics STA 2023Finals Review (Tests 4, 5,
6) Questions and
Complete Solutions
Graded A+
The purpose of statistical inference is to provide information about the - Answer: population based upon
information obtained from a sample
A survey of 400 non-fatal accidents showed that 189 involved the use of a cell phone. Determine a point
estimate for p, the population proportion of non-fatal accidents that involved the use of a cell phone. -
Answer: 0.473
A media poll of 500 air travelers surveyed in national airports found that 370 favor tighter security
procedures in boarding planes. Construct a 90% confidence interval for the proportion of all air travelers
who are in favor of tighter security procedures. - Answer:
It has been determined with 95% confidence that the proportion of on-line students at SPC who live in
Pinellas County is between 0.73 and 0.77.
Determine the margin of error associated with this confidence interval. - Answer: ±0.02
It has been determined with 95% confidence that the proportion of on-line students at SPC who live in
Pinellas County is between 0.73 and 0.77.
Determine the sample proportion of on-line SPC students who live in Pinellas County. - Answer: 0.75
A survey of 280 homeless persons showed that 63 were veterans. Construct a 90% confidence interval
for the proportion of homeless persons who are veterans. - Answer: (0.184, 0.266)
, Determine the confidence level for confidence interval shown in the figure below. Choices in
percentages are: 98, 95, 90, 80, 99 - Answer: 80%
A survey of 300 union members in New York State reveals that 112 favor the Republican candidate for
governor. Construct a 90% confidence interval for the percentage of all New York State union members
who favor the Republican candidate. - Answer: (32.7%, 41.9%)
What is the approximate sample size required to estimate the percentage of Americans who have
earned a college degree to within 2%, with 95% confidence?
Recall: the worst case scenario would assume that p = 0.5 - Answer: 2401
What will happen (other things being equal) if you decrease the confidence level for a given confidence
interval? - Answer: It will be narrower
In a survey of 500 residents, 300 were opposed to the use of photo-cops for issuing traffic tickets.
Find the margin of error that corresponds to a 95% confidence interval for the proportion of residents
that are opposed to the use of photo-cops for issuing traffic tickets. - Answer: 0.04
What will happen (other things being equal) if you increase the sample size used to construct a given
confidence interval? - Answer: It will be narrower
An article estimates, with 90% confidence, that the proportion of elementary school teachers who are
female is 82%. The article also states the maximum error of their estimate is 3%.
Determine the resulting 90% confidence interval for the proportion of elementary school teachers who
are female. - Answer: (79%, 85%)
In a random sample of 60 computers, the mean repair cost was $150 with a standard deviation of $36.
Construct a 90% confidence interval for the population mean. - Answer: ($142, $158)
An environmental journal discussing current water usage within the US reports, with 95% confidence,
the average number of household gallons used per person per day is between 82 and 88. The study was
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