Scores on an IQ Test Are Normally Distributed $\sigma = 15$

Scores on an IQ test are normally distributed. A sample of 19 IQ scores had standard deviation s=9 . The developer of the test claims that the population standard deviation is $\sigma = 15$ Do these data provide sufficient evidence to contradict this claim? Use the $\alpha = 0.05$ level of significance.

A) Reject $H _ { 0 } .$
The population standard deviation appears to differ from 15 .
B) Do not reject $H _ { 0 }$
There is insufficient evidence to conclude that the population standard deviation differs from 15 .

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