Confidence Intervals: Exercises

Confidence Intervals
Miscellaneous on-line topics for
Finite Mathematics 2e

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Utility: Normal Distribution Utility
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Following is a little table of $z-$values. For a separate window showing values of $t_{α/2},$ press here. (You can also use the $t$_infinity row in place of the $z-$table.)

$\color{blue}{z_{.1}}$	$\color{blue}{z_{.05}}$	$\color{blue}{z_{.025}}$	$\color{blue}{z_{.01}}$	$\color{blue}{z_{.005}}$	$\color{blue}{z_{.001}}$	$\color{blue}{z_{.0005}}$
$1.282$	$1.645$	$1.960$	$2.326$	$2.576$	$3.090$	$3.291$

1. Teenage Entertainment A random sample of 49 teenagers was surveyed, and the average number of movies that they had rented in the past week was $1.9,$ with a sample standard deviation of $0.5.$ Construct a $95%$ confidence interval for the average number of movies rented by teenagers in a week. (Round answers to $2$ decimal places.)

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(b) Your regional manager at Sonic Video responds with the following memo:

TO: G.E.Cost
FROM: V. Meluzio
SUBJECT: Your job status
GC: Once again, you have failed to provide the accurate information we need (where was it that you got that $A$ in a quantitative methods?) I thought you had hit rock bottom after the "Mars Attacks" debacle, but it now appears that you have started to dig. Indeed, you might recall, in the very dim recesses of your mind, that I specifically requested an error range of no more than $± 0.1$ in your estimate of the number of movies per teenager per week, and you came up with an error almost $50%$ too high. Kindly submit a confidence interval with a spread of no more than $± 0.1$ with a $95%$ confidence level by tomorrow at 9 am. or you are fired.

How large a sample should you now poll in order to save your job?

Confidence Intervals Miscellaneous on-line topics for Finite Mathematics 2e

Confidence Intervals
Miscellaneous on-line topics for
Finite Mathematics 2e