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Statistics for Decision- Making in Business - Maricopa Community ...

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In the second section, we can check up to two boxes, <strong>in</strong> the event that we would like to f<strong>in</strong>d an<br />

area between two po<strong>in</strong>ts. We can either enter values as z-scores or as raw data values ( ). To f<strong>in</strong>d<br />

the probability of a value greater than, we click the grey box to select:<br />

The probability of such an event is displayed <strong>in</strong> the “prob” box. If we have two values entered<br />

and both boxes checked, then the “probability between” these two values is displayed. Isn‟t this<br />

much more <strong>in</strong>tuitive and convenient than us<strong>in</strong>g tables<br />

NOTE: One limitation of the above applet is that<br />

a bit of f<strong>in</strong>agl<strong>in</strong>g.<br />

values rounded to two decimal places require<br />

Homework Problems – 5.2<br />

Use the applet mentioned <strong>in</strong> this section to complete these exercises. You are not required to use<br />

the standard normal table.<br />

1. In the United States, IQ‟s are normally distributed with and .<br />

a. What is the probability that a person has an IQ lower than 130<br />

b. What is the probability that a person has an IQ between 80 and 110<br />

c. What is the probability that a person has an IQ between 50 and 70<br />

d. What is the probability that a person has an IQ above 120<br />

2. In the UK, birth weights are approximately normally distributed with lbs. and<br />

lbs. (SOURCE: http://www.healthknowledge.org.uk).<br />

a. F<strong>in</strong>d and expla<strong>in</strong> the real-world mean<strong>in</strong>g of ( ).<br />

b. F<strong>in</strong>d and expla<strong>in</strong> the real-world mean<strong>in</strong>g of ( ).<br />

c. F<strong>in</strong>d and expla<strong>in</strong> the real-world mean<strong>in</strong>g of ( ).<br />

d. F<strong>in</strong>d and expla<strong>in</strong> the real-world mean<strong>in</strong>g of ( ).<br />

e. What weight is such that 20% of <strong>in</strong>fants weight less than this amount (HINT:<br />

You can still use the calculator applet.)<br />

3. In a recent years, Scholastic Aptitude Test (SAT) scores <strong>for</strong> all college-bound seniors <strong>in</strong><br />

the United States was such that po<strong>in</strong>ts and po<strong>in</strong>ts (SOURCE:<br />

http://www.collegeboard.com) .<br />

a. 50% of students scored less than how many po<strong>in</strong>ts<br />

b. 50% of students scored more than how many po<strong>in</strong>ts<br />

c. In order to be <strong>in</strong> the top 10% of SAT-takers, what score would one have to<br />

achieve<br />

d. What score do the lowest 10% score between<br />

e. The middle 50% of students scored between what two values<br />

4. Sketch a normal distribution and . Label the mean, standard deviations,<br />

standard deviations, and standard deviations.<br />

<strong>Statistics</strong> <strong>for</strong> <strong>Decision</strong>-<strong>Mak<strong>in</strong>g</strong> <strong>in</strong> Bus<strong>in</strong>ess © Milos Podmanik Page 179

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