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grei
Posts:
128
Registered:
11/27/12


Re: Help with word problems
Posted:
Apr 9, 2013 11:20 AM


> 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 http://www.mathsisfun.com/data/standardnormaldistributiontable.html) 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



