# Chi square

A manufacturer of phone batteries claims that his batteries' lives are approximately normally distributed with a standard deviation equal to 0.9 years. If 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 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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