# Test For Random Occurrence

• Dec 4th 2010, 04:02 PM
avovk
Test For Random Occurrence
Hello,

I have a test on monday 12/6/10 and in the review I cannot answer this question. I would appreciate it very much if someone could help me.

After many years, the mean tensile strength of cables produced by the XYZ company was determined to be 1000 lb. with the standard deviation of 100 lb. A new technological process has been implemented. Newly manufactured cables were sampled for tensile strength, and it was found that in a sample of size 100, the mean happened to be 1100 lb. Is this a random occurrence, or the new technology truly improves the performance? To answer this question consider the following hypotheses:

H 0: u = 1000

H 1: u > 1000

Thank you,
Alex
• Dec 4th 2010, 04:23 PM
pickslides
What will you use as your test statistic and your level of significance?

I would use $t$ and $\alpha = 0.05$
• Dec 4th 2010, 04:34 PM
avovk
I'm actually not sure about that. There is some formula with the z-index that is used to solve this.
• Dec 4th 2010, 04:38 PM
pickslides
Quote:

Originally Posted by avovk
I'm actually not sure about that. There is some formula with the z-index that is used to solve this.

as $n$ gets large enough $t\rightarrow z$ so the answer could be the same either way.
• Dec 4th 2010, 04:56 PM
avovk
This is what I have. It received half credit.

http://img194.imageshack.us/img194/3964/tipw.png