Chi square
A phone battery manufacturer claims that his battery lives are approximately normally distributed with a standard deviation equal to 0.9 years. Suppose a random sample of 10 of these batteries has a standard deviation of 1.2 years. Do you think that the standard deviation is greater than 0.9 years? Use a 0.05 level of significance.
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Dr Math
Answer is NO. These is no reason to doubt, that the standard deviation is 0.9 year
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