SOLUTION: PROBLEM 3 Mall security estimates that the average daily per-store theft is exactly $250, but wants to determine the accuracy of this statistic. The company researcher takes a sa

Question 366430: PROBLEM 3
Mall security estimates that the average daily per-store theft is exactly $250, but wants to determine the accuracy of this statistic. The company researcher takes a sample of 81 clerks and finds
X(BAR) = $210
S = $40.
a) Test at α = .001
b) Construct a 90% CIE of μ
I Tried this for Part a
Z = and I got 9. From there I get confused and don't know what to do next or even if my first answer for part a is right.
Any help would be greatly appreciated. If you can explain how you got the answer that would be even better.

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Mall security estimates that the average daily per-store theft is exactly $250, but wants to determine the accuracy of this statistic. The company researcher takes a sample of 81 clerks and finds
X(BAR) = $210
S = $40.
a) Test at alpha = .001
b) Construct a 90% CIE of u
Feedback:
Part a::::
Ho: u = 250
Ha: u is not equal to 250
-----
I use a t-statistic for mean problems involving sample size.
-----
The critical values are +/-3.416337
The test statistic is t(210) = (210-250)/(40/ sqrt(81)) = -9
-----
Conclusion: Since the ts is in the rejection interval,
reject Ho.
===========================
Part b:::
Construct a 90% CIE of u
---
x=bar = 210
E = 1.6641 = 7.3961
---
90% CIE: 210-7.3961 < u < 210+7.3961
90% CIE: 202.6039 < u < 217.3961
=======================================
Let me know if this helps.
=======================================
Cheers,
Stan H.
----

RELATED QUESTIONS
Mall security estimates that the average daily per-store theft is less than$250, but... (answered by stanbon)

Jessica sells T-shirts from her small kiosk in the shopping mall. On average, she sells... (answered by josmiceli)

The chief of security for the Mall of the Dakotas was directed to study the problem of... (answered by stanbon)

Thank your for your continued guidence and help in my pursuit of understanding... (answered by stanbon)

please help...i've done several problems but i'm stuck on a couple... Suppose that 30%... (answered by stanbon)

3. Marginal cost. Suppose the daily cost, in hundreds of dollars, of producing x... (answered by CPhill)

A store specializing in mountain bikes is to open in one of two malls. If the first mall (answered by Boreal)

I have a word problem. "A tour bus serving 400 customers a day charges $5 per person.... (answered by jsmallt9)

A salesperson finds that her saStules average 40 cases per store when she visits 30... (answered by KMST)