Math Is Fun Forum

NEKA

Member

Registered: 2006-01-02

Posts: 9

Last problem in Stats

An executive at Westinghouse drives from his home in the suburbs near
Pittsburgh to his office in the center of the city. The driving times
can be approximated by the normal distribution,with a mean of 35 minutes
and a standard deviation of 8 minutes.

a.What percent of the days will it take him 30 minutes or less to drive
to work?

b.What percent of the days will it take him 40 minutes or more to drive
to work?

c.Explain to the executive why the probability is nearly 0 that it will
take him exactly 40 minutes to get to work.

d.The executive did not understand your answer to part c. How would you
estimate the percent of days it takes 40 minutes to drive to
work?(Hint:Within what range of values would the times be rounded to
40?)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Last problem in Stats

Hi NEKA;

a)

b)

c)
The reason is the normal distribution is a continuous distribution. It amounts to an area under a curve. Asking for exactly 40 minutes is asking what area does a line have.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.