Exam 9: Estimating the Value of a Parameter Using Confidence Intervals

Explain the Role of Margin of Error in Constructing a Confidence Interval -A 90% confidence interval for the mean percentage of airline reservations being canceled on the day of the flight is (1.2%, 4.5%). What is the point estimator of the mean percentage of reservations that are canceled on the day of the flight

Choose the one alternative that best completes the statement or answers the question. -As the level of confidence increases the margin of error decreases.

State the Properties of Student s t-Distribution -A computer package was used to generate the following printout for estimating the sale price of condominiums in a particular neighborhood. What assumptions are necessary for any inferences derived from this printout to be valid?

Provide an appropriate response. -A survey of 1010 college seniors working towards an undergraduate degree was conducted. Each student was asked, "Are you planning or not planning to pursue a graduate degree?" Of the 1010 surveyed, 658 stated that they were planning to pursue a graduate degree. Construct and interpret a $98 \%$ confidence interval for the proportion of college seniors who are planning to pursue a graduate degree.

Determine the Sample Size Necessary for Estimating the Population Mean within a Specified Margin of Error - $\mathrm { E } = 20 , \sigma = 175 , ( 1 - \alpha ) = 0.99$

Provide an appropriate response. -Construct a $98 \%$ confidence interval for the population mean, $\mu$ . Assume the population has a normal distribution. A study of 14 car owners showed that their average repair bill was $\$ 192$ with a standard deviation of $\$ 8 .$

Provide an appropriate response. -True or False? If no estimate of $p$ exists when determining the sample size, we can use $0.5$ in the formula to get a value for $\mathrm { n }$ .

Choose the one alternative that best completes the statement or answers the question. -In a sample of 10 randomly selected employees, it was found that their mean height was $63.4$ inches. From previous studies, it is assumed that the standard deviation, $\sigma$ , is $2.4$ . Compute the $95 \%$ confidence interval for $\mu .$

Provide an appropriate response. -Many people think that a national lobby's successful fight against gun control legislation is reflecting the will of a minority of Americans. A previous random sample of 4000 citizens yielded 2250 who are in favor of gun control legislation. How many citizens would need to be sampled if a $90 \%$ confidence interval was desired to estimate the true proportion to within $3 \%$ ?