# Thread: Test For Random Occurrence

1. ## 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

2. What will you use as your test statistic and your level of significance?

I would use $t$ and $\alpha = 0.05$

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

4. 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.

5. This is what I have. It received half credit.