Question 1201663
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Answers:<ol type="a"><li><font color=red>284 and 316</font></li><li><font color=red>268 and 332</font></li><li><font color=red>252 and 348</font></li></ol>

Explanation:


We use the Empirical Rule.
Some textbooks call it the 68-95-99.7 rule but I don't think it's as catchy of a name.


The rule has 3 properties:<ul><li>roughly 68% of the normal distribution is within 1 standard deviation of the mean.</li><li>roughly 95% of the normal distribution is within 2 standard deviations of the mean.</li><li>roughly 99.7% of the normal distribution is within 3 standard deviations of the mean.</li></ul>
*[illustration Screenshot_125.png]


For part (a), the work shown would be something like this
mu - 1*sigma = 300 - 1*16 = 284
mu + 1*sigma = 300 + 1*16 = 316
Roughly 68% of the observations are between 284 and 316.


For part (b), we have
mu - 2*sigma = 300 - 2*16 = 268
mu + 2*sigma = 300 + 2*16 = 332
Roughly 95% of the observations are between 268 and 332.


For part (c), the phrasing "practically all" means "practically 100%" which is close enough to 99.7%
mu - 3*sigma = 300 - 3*16 = 252
mu + 3*sigma = 300 + 3*16 = 348
Roughly 99.7%, aka practically all, of the observations are between 252 and 348.
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