Im Having issues with the following Question in some of my stats review, i don't think i really understand how to solve what they are asking for.
for A)
.01% = 0.0001, so Zscore= -3.7
However, after that, i don't really understand where to go from there, to determine if the the standard deviation exceeded a certain value in regards to a significance level.
Can anyone help shed some light on these 2 parts of the question for me? thanks
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An environmental testing company recently initiated new quality control methods to test recreational water samples for harmful/infectious bacteria. The data presented in the table below refer to MCLG (mg/L) taken before and after quality control methods were
introduced. Treat samples as coming from normally distributed populations.
Before Quality Control: n=15 s=1.25mg/L
After Quality Control : n=18 s=0.85mg/L
a) Test at the 0.01% level of significance whether the standard deviation before the quality control method was introduced significantly exceeded 1.0 mg/L.
b )Test at the 1% level of significance whether the standard deviation after the quality control method was introduced became less than 1.25 mg/L
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I appreciate any help or insight on these questions. Im not looking for the answers to finish the review, i just dont understand how to solve the question, and i need to know it!
Thanks
-Shane