Probability distributions

Kiwigirl

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Feb 27, 2006
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1. In a warehouse, accidents have been taking place at the rate of 2 every 3 months.
a) What probability distribution is most likely to model the number of accidents in a 3 month period (This is be selected from either the Binomial, Poisson or normal distribution)? Explain why you have made your choice and give any parameter(s) for the distribution.
b) Find the mean and standard deviation of the number of accidents per year
c) What is the percentage of months with no accidents?
d) If a month is chosen at random, find the probability of at least one accident.

2. A traffic officer has a concealed radar unit that she uses to measure the speed of traffic crossing a bridge. She finds that the mean speed is 84km/h and the standard deviation is 5km/h.
a) What probability distribution is most likely to model the speed of the traffic crossing the bridge? Explain why you made your choice and give any parameter(s) for your distribution.
b) If the speed limit on the bridge is 90km/h, find out how many out of 200 cars she would expect to find to be breaking the limit.
 
Kiwigirl said:
1. In a warehouse, accidents have been taking place at the rate of 2 every 3 months.
a) What probability distribution is most likely to model the number of accidents in a 3 month period (This is be selected from either the Binomial, Poisson or normal distribution)? Explain why you have made your choice and give any parameter(s) for the distribution.
b) Find the mean and standard deviation of the number of accidents per year
c) What is the percentage of months with no accidents?
d) If a month is chosen at random, find the probability of at least one accident.
a) Poisson. Occurrences in a given period of time suggests Poisson. \(\displaystyle \lambda\)=2 for a 3-month period. \(\displaystyle \lambda\) = 8 for years. \(\displaystyle \lambda\) = (2/3) for a single month.
b) Pretty easy for the Poisson. You do this one.
c) Pr(0) using \(\displaystyle \lambda\) = 2/3
d) 1-Pr(0) using \(\displaystyle \lambda\) = 2/3
 
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