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Dear sir,
I would like to ask you a few basic questions on statistic about normal distribution. I'm currently taking a course in computer simulation and I have came across several passages in textbook like below:
the number of tasks are assumed to be bimodel. 80% of the tasks come from a high normal distribution (high value tasks) and 20% of the tasks come from a low normal distribution (low value tasks). High valued tasks are assumed to be, on average, 10x more important than low value jobs.
I'm not clear whether my understanding is correct. As far as I'm concerned, a normal distribution has 2 parameters the mean and the standard deviation. If, as the example above, the high value tasks are 10x more than low value tasks, I presume: the mean parameter for low value task is 1, and the mean parameter for high value task is 10. But what about the standard deviation? Do we assume the standard deviation is 1 for both high value and low value task?
Here is also another example:
Under light traffic load, between 10 and 20 requests per node per hour are generated, while twice as many requests are generated under heavy load. All parameters are distributed normally between the high and low values.
The questions is what parameters should I consider here? I'd assume that you need two different normally distributed numbers for both light traffic load and heavy load? However, what value should I put in for standard devation?
To get a normally distributed number with 10 and 20, the normal distribution mean is 15 with standard 5?
However, I don't think normal distribution will give me gurante that a number will be a certain range (unlike uniform distribution). I'm very much confused here. I'd really appreciate if you could clarify the issues. Thank you.
regards,
Am
A good way to do it would be to say that it is from a normal
that goes from 10 to 20 and for the heavy to say the normal is
20 to 40.
If it is assumed that all of the traffic is distributed between the high and low values, for a normal distribution, it is usually assumed to be ±3σ from the averge, µ.
If you had some probability involved, you could look it up on a normal distribution table (it sounds like a two sided test).
For ±σ, it is 84.13%.
For 2σ, it is 97.72².
For 3σ. it is 99.56%. That is the most common one in industry use today.
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Scott A Wilson
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