A transportation worker takes a simple random sample of 135 toll booth receipts for one day and finds that the mean is $8.64 with a standard deviation of $2.19. What is the 99% confidence interval for the mean amount of all the receipts that day?
A. ($8.15, $9.13)
B. ($8.27, $9.01)
C. ($8.51, $8.77)
D. ($8.60, $8.68)

Question

A transportation worker takes a simple random sample of 135 toll booth receipts for one day and finds that the mean is $8.64 with a standard deviation of $2.19. What is the 99% confidence interval for the mean amount of all the receipts that day?
A. ($8.15, $9.13)
B. ($8.27, $9.01)
C. ($8.51, $8.77)
D. ($8.60, $8.68)

anonymous · Answer

@jim_thompson5910 can you help me here too?

jim_thompson5910 · Answer

for a 99% CI, what is the critical value (z*) ?

anonymous · Answer

I dont get it :'(

jim_thompson5910 · Answer

do you know the formula to find the confidence interval (CI) ?

anonymous · Answer

no

jim_thompson5910 · Answer

it's a long process with a lot of steps, so I recommend reading this http://stattrek.com/estimation/confidence-interval.aspx that article should help. If not, then let me know

anonymous · Answer

ok so i think i got it....is it A($8.15, $9.13)?

jim_thompson5910 · Answer

I got the same as well. Nice work.

anonymous · Answer

yay thanks :D

jim_thompson5910 · Answer

np