Does anyone know AP Stat?

Test Preparation AP Mathematics & Computer Science
1

<p>A newly hired telemarketer is told he will probably make a sale on about 12% of his phone calls. The first week he called 200 people, but only made 10 sales. Should he suspect he was misled about the true success rate? Explain.</p>

<p>Answer key says: The mean number of sales should be 24 with SD 4.60. Ten sales is more than 3.0 SDs below the mean. He was probably mislead.</p>

<p>I get the part where it says that mean is 24 and that SD is 4.60, but I don't understand when they say that "ten sales is more than 3.0 SDs below the mean... I have no idea what that means...
Can anyone help me understand? Maybe cuz i don't understand what standard deviation means? i dunno...</p>

2

<p>From what I understand, standard deviation is the average distance away from the mean for all the values, and three standard deviations is huge. If you were in college being three standard deviations away from the average, your grade would probably be a F. (hope that gives some kind of context)</p>

3

<p>The probability of getting 10 sales if the true mean is 24 is 3 standard deviations away, which is equal to 0.1% as seen in this chart.</p>

<p><a href=“http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Standard_deviation_diagram.svg/325px-Standard_deviation_diagram.svg.png[/url]”>http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Standard_deviation_diagram.svg/325px-Standard_deviation_diagram.svg.png&lt;/a&gt;&lt;/p&gt;

<p>Due to this unlikeliness, he was mislead.</p>

4

<p>Calculate sd by using the formula sqrt(pq/n)
Where p is the percentage of successes, q is the percentage of failures and n is the sample size</p>

5

<p>I believe they are discussing z-score. (I’m in AP Stats right now) thats what tells you how many standard deviations something is above/below the mean</p>