Question

Please help me with this statistics question, I will give you a super shiny shiny medal! Thank you :) And please be thorough, I would like to learn :)

Answer 1

so I know n = 51 and s = 0.080 and xbar = 0.15.

Answer 2

so the confidence level is 0.90 so (sorry its messy) using a mouse

Answer 3

0.15 - 0.045(0.08/(sqrt)51)?

Answer 4

wait a minute. I think i know why I'm doing this incorrectly.. the critical value is 0.05 and I was supposed to put 0.05 -> 1-0.05 = 0.95 and INVnorm: 0.95, 0, 1 = 1.644853626.. oops

Answer 5

so the lower bound I got 0.15 - 1.644853626 ( 0.080/sqrt51) = 0.1315739538

Answer 6

Yeah, Z crit for 90% confidence is 1.64. After doing a few you can memorize them.

from http://www.ucd.ie/statdept/classpages/introquantmeths/introqmchp12.pdf
The level of confidence determines the z critical value.
99% 2.58
95% 1.96
90% 1.645

Answer 7

oh.. That is a really good idea for me to memorize them, thank you so much! Thank you for the link! (It more direct than what I learned!)

Answer 8

and for my upper bound: 0.15 + 1.644853626 ( 0.080/sqrt51) = 0.1684260462

Answer 9

Looks reasonable.

Answer 10

C. The lower bound is 0.132 and the upper bound is 0.168 The researcher is​ 90% confident that the population mean BAC is in the confidence interval for drivers involved in fatal accidents who have a positive BAC value.


so 0.15 is inside the lower and upper bound so it's inside the confidence interval.

Answer 11

Ahh thank you so much for helping me!! Im so sorry for taking your time with my math questions.

Answer 12

Welcome.