Hypothesis prob: A soft-drink machine is 'out of control' if

[machtsichtbar]

A soft-drink machine is said to be out of control if the variance of the contents exceeds 1.15 deciliters. If a random sample of 25 drinks from this machine has a variance of 2.03 deciliters, does this indicate at the 0.05 level of significance that the machine is out of control? Assume that the contents are approximately normally distributed.

Not sure what is the H0. Variance =/>=/< 1.15?

 

[royhaas]

The null hypothesis is one of equality.

 

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Is that a general rule? Also, how do I dicide what the alternative hypothesis is?

 

[tkhunny]

The "general rule" is to decide what it is you are testing. This machine is "out of control" in either direction, too high or too low. If you're fine with too low and wish to test only for too high, that's a different matter.