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Topic: Help with word problems
Replies: 3   Last Post: Apr 9, 2013 11:20 AM

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Posts: 132
Registered: 11/27/12
Re: Help with word problems
Posted: Apr 9, 2013 11:20 AM
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> Need help with these word problems, pretty hard.
If you know the DEFINITIONS, they are actually pretty easy.

> 1. Airline Delays. Suppose you are a scheduler for a
> major airline, analyzing a distribution of flight
> delays (departures) during one day at an airport. The
> distribution of delay times has the following
> properties: The mean delay is 10 minutes, the median
> delay is 6 minutes, the mode is the distribution is 0
> minutes, and the maximum delay is 25 minutes.
> a. What percentage of flights were delayed less than
> 6 minutes?
> b. What percentage of flights were delayed more than
> 6 minutes?

Do you know what "median" means? If you do, then these two questiohs are trivial.

> 2. Body Mass Index (BMI). The body mass indices of
> American men between ages 30 and 50 are normally
> distributed with a mean of 26.2 and a standard
> deviation of 4.7.
> a. Determine the standard score and percentile of a
> BMI of 22.

Given a normal distribution with mean m and standar deviation s, the "standard normal variable corresponding to variable x is z= (x- m)/s.

So z= (22- 26.2)/4.7. Look up the probability on a Normal distribution table (There is a good one at and convert to a percentile.

> b. Determine the standard score and percentile of a
> BMI of 28.

Same thing. z= (26- 26.2)/4.7

> c. Several health organizations have declared that
> men with a BMI of 25 or greater are overweight and
> that men with a BMI of 30 or greater are obese. What
> percentage of American men are overweight? obese?

z= (26- 26.2)/4.7. Look that up on a table

z= (30- 26.2)/4.7

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