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Thread: Confidence level

  1. #1
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    Confidence level

    Hello,

    Simulating a queue doing 100 times. Confidence level is 95% and Confidence interval is (413s,425s) for average response time.
    What is standard division?

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  2. #2
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    Re: Confidence level

    Assuming the question is instead "What is the standard deviation?"

    Hint: Given a high number of samples, we can assume the graph is approx. a normal distribution. From here, we can calculate the z-score for a confidence level of 95%. Can you take it from here?
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  3. #3
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    Re: Confidence level

    Quote Originally Posted by MacstersUndead View Post
    Assuming the question is instead "What is the standard deviation?"

    Hint: Given a high number of samples, we can assume the graph is approx. a normal distribution. From here, we can calculate the z-score for a confidence level of 95%. Can you take it from here?
    Thank you,
    Attached Thumbnails Attached Thumbnails Confidence level-fdfs.jpg  
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  4. #4
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    Re: Confidence level

    Just to confirm, you have to use the z-score for the final calculation of the standard deviation. I didn't want to give away too much so you could figure out the rest of the answer. Let me know if you need more help on that.
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  5. #5
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    Re: Confidence level

    Thanks, with which formula ?
    Now we have n = 100 , Confidence level is 95% and confidence interval is (413s,425s).
    With which formula we can calculate SD?
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  6. #6
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    Re: Confidence level

    With a calculated z-score of 1.96, this means we have a graph like this


    ie. The upper limit is 1.96 standard deviations from the mean. The lower limit is -1.96 standard deviations from the mean.

    From here, you should be able to answer the following:
    (i) What is the mean of your confidence interval? (call this x)
    (ii) What is the standard deviation from the mean? ie. If 1.96 standard deviations is the difference between x and 425s, what is 1 standard deviation?

    Answer i and ii and you are done. Once you understand the process, feel free to use a compact formula like 1 SD = (b-a)/(z-score) where (a,b) is your confidence interval.
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  7. #7
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    Re: Confidence level

    Quote Originally Posted by MacstersUndead View Post
    1 SD = (b-a)/(z-score) where (a,b) is your confidence interval.
    Typo. 1 SD = (b-(mean))/(z-score)

    where the mean is a + (b-a)/2
    Last edited by MacstersUndead; Jan 5th 2017 at 11:49 AM.
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