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**rmdenis** · February 15th 2010, 04:10 PM

I need a step by step walk through SAT verbal scores are normally distributed with a mean of 489 and a standard deviation of 93. What percent of the scores lie between 303 and 582?

**matheagle** · February 15th 2010, 05:17 PM

$P(303<X<582)=P\left( {303-489\over 93} <Z< {582-489\over 93}\right)$

One could add in a correction factor of $\pm .5$ but that won't change much here.
Plus we don't know if you were supposed to include the endpoints anyhow.

**rmdenis** · February 21st 2010, 06:49 AM

Thanks, new question: A horse race has 13 entries. Assuming that there are no ties, what is the probability that the five horses owned by one owner will come in first, second, third, fourth and fifth?

**matheagle** · February 21st 2010, 06:52 AM

If you don't care which of the five come in which order, it's just hypergeometric.

**rmdenis** · February 21st 2010, 02:17 PM

**matheagle** · February 21st 2010, 02:28 PM

${ {5\choose 5} {8\choose 0}\over {13\choose 5}}$

OR, if you prefer conditional probabilities......

$\left({5\over 13}\right)\left({4\over 12}\right)\left({3\over 11}\right)\left({2\over 10}\right)\left({1\over 9}\right)$

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explain the entire problem as if I was 8 yrs old