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# Normal Distribution Help Watch

1. Slow Sid takes Y minutes to install a dish which is normally distributed. It is known that p(Y<170) = 0.14 and P(Y>200)=0.03.

Find the mean and standard deviation of Y.
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4. (Original post by Tempa)
Slow Sid takes Y minutes to install a dish which is normally distributed. It is known that p(Y<170) = 0.14 and P(Y>200)=0.03.

Find the mean and standard deviation of Y.
Using your normal distribution tables, you want to find z, such that P(Z< z) = 0.14, similarly the second one.

One value minus the other gives you the number of standard deviations that the interval 170 to 200 covers, and hence you can work out the s.d.

Post some working if you're still stuck.
5. The distances travelled to work D km, by the employees at a large company are normally distributed with D ˜ N (30, 8 squared)

(a) Find the upper quartile, Q3, of D.

(b) Write down the lower quartile, Q1, of D.

(c) An outlier is defined as any value of D such that D < 8.4 or D > 51.6
An employee is selected at random.
Find the probability that the distance travelled to work by this employee is an outlier.
______________________________

For (a) you do P (D < Q3) and make it equal to something that’s what someone told me! I was wondering why the sign was < and not > to find the P (D < Q3)?

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Updated: December 19, 2010
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