Question 1149653
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Given information
The value "11 years" is not used at all. 
phat = 0.25 is the sample proportion
n = 1800 is the sample size


At 99% confidence, the critical z value is approximately z = 2.576
I used <a href="http://www.sjsu.edu/faculty/gerstman/StatPrimer/t-table.pdf">this table</a> to find the critical z value. A similar table should be found in the appendix section of your textbook. 
If you choose to use the table I have linked, then locate the bottom row that shows "99% confidence level". Afterward look just above that to find 2.576
Alternatively you can use the invNorm function on your TI83 or TI84 calculator to get the same approximate value.


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Lets compute the lower bound (L) and the upper bound (U) of the confidence interval. 


L = lower bound of confidence interval
L = phat - z*sqrt(phat*(1-phat)/n)
L = 0.25 - 2.576*sqrt(0.25*(1-0.25)/1800)
L = 0.22370881009412
L = 0.22


U = upper bound of confidence interval
U = phat + z*sqrt(phat*(1-phat)/n)
U = 0.25 + 2.576*sqrt(0.25*(1-0.25)/1800)
U = 0.27629118990588
U = 0.28


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The 99% confidence interval is <font color=red size=4>(0.22, 0.28)</font>
This means at 99% confidence we can say 0.22 < p < 0.28, where p is the population proportion of immigrants selected for grand jury duty. 
This is over the time span of the 11 years mentioned. 
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