
Probability and Statistics Basic Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
December 31st, 2016, 06:47 AM  #1 
Newbie Joined: Dec 2016 From: Pakistan Posts: 3 Thanks: 0  Two questions related to normal distribution
A telephone exchange receives, on average, 5 calls per minute. Find the probability that in a 20 minute period no more than 102 calls are received Exactly 90 calls are received and A radioactive element disintegrates such that it follows a Poisson distribution. If the mean number of particles emitted is recorded in a 1 second interval as 69, evaluate the probability of: Less than 60 particles are emitted in 1 second. Between 65 and 75 particles inclusive are emitted in 1 second. 
December 31st, 2016, 01:49 PM  #2 
Global Moderator Joined: May 2007 Posts: 6,235 Thanks: 497 
First question: Unless you assume a Poisson distribution, there is not enough information. To use a normal approximation, you need a variance. To get a probability for exactly 90, use the exact formula (assuming Poisson). Second question: For a Poisson distribution the variance equals the mean. Look up table of normal distribution to get the probabilities for the particular mean and variance. 

Tags 
distribution, normal, questions, related 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Normal distribution: a probability distribution?  froydipj  Probability and Statistics  3  February 29th, 2016 05:35 PM 
Multivariate normal distribution and marginal distribution  nakys  Advanced Statistics  0  October 3rd, 2013 08:27 AM 
Normal Distribution  esther_17  Algebra  9  March 10th, 2012 07:53 PM 
LogNormal Distribution Questions!  Will57  Advanced Statistics  0  February 26th, 2012 11:29 PM 
Poisson distribution and binomial distribution questions  latkan  Advanced Statistics  1  May 11th, 2009 05:49 AM 