Passion Distribution

T

Teresa8057

New member
Joined
Jul 24, 2020
Messages
10
Suppose 10 drives per day fail in data center, on average how many drives do we expect to fail over the next 100 days. The average and variance equal to λ, my answer is 1000, but I am not certain, looking for suggestions.
 
I have no idea why you mention "average and variance". If 10 fail per day and the failures are independent (each failed drive is repaired but a repaired drive is just as likely as any other to fail the next day) then the expected number of failed drives over the next 100 days is 10*100= 1000. (Assuming that you are including the same drive fail repeatedly as different failures.)
 
Let me reorganize the problem,
Assume 10 drives per day fail on average, assume the drive failures obey a Possion distribution, the average and variance of Possion distribution is λ, on average how many drives are expected to fail over the next 100 days.
 
Teresa8057 said:
I also think it is 1000. This question is little tricky.
Click to expand...
Why? 10 per day for 100 days is 1000. Is that really tricky?

(10 + 10 + 10 + ... + 10) = 100(10) = 1000. Why would you expect any other number?
 
The question is not tricky. It is asking you to know and to understand one property of the Poisson Distribution. It is perfectly scalable. Hardly any arithmetic required.
 
I have another problem, ask the probability that more than 1200 drives fail over the next 100days, my solution is Possion distribution, but how to put the parameter 100days in the equation.
 
Remember that "perfectly scalable"?

10 drives fail in 100 days. If the question REALLY says 1200 drives in 100 days, please don't do any arithmetic. It is a very, VERY small number.

Does it say 1200 drives in 1000 days? Still a very small number.
 
Assume 10 drives per day fail on average, assume the drive failures obey a Possion distribution, the average and variance of Possion distribution is λ. The probability of 1200 drives expected to fail in next 100 days.
 
Teresa8057 said:
Assume 10 drives per day fail on average, assume the drive failures obey a Possion distribution, the average and variance of Possion distribution is λ. The probability of 1200 drives expected to fail in next 100 days.
Click to expand...
You don't seem to be moving forward. Repeating the question is sometimes useful, but it will not magically provide the desired answer. You must apply your knowledge to bridging the gap between problem statement and solution.

What is a Poisson Probability Distribution? How does it work? What does "scalable" mean? How are probabilities calculated with a Poisson Probability Distribution? Can you add up a bunch of probabilities with one go or do you have to calculate them all separately? Is it continuous or discrete?

How can you apply what you know to approach a valid response?
 
You must log in or register to reply here.
Top