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mean and standard deviation
Message posted by b king on January 18, 2001 at 12:00 AM (ET)
I submitted question about. mean and standard deviation, please not that email address is kingb36@home.com
READERS RESPOND:
(In chronological order. Most recent at the bottom.)
Re: mean and standard deviation
Message posted by Phil on January 21, 2001 at 12:00 AM (ET)
Like the previous post said, the question most likely is referring to the normal distribution. Look in most any statistics text under normal distribution. You need to find the equation for "Z" or "Z-score". Once you find that part of the book, you are in the ballpark.
Re: mean and standard deviation
Message posted by Phil on January 21, 2001 at 12:00 AM (ET)
Z = (x - mean)/(std. dev.)In your case: z = (448-450)/2 = -1
Now, with z = -1, look up the probability that z < -1 in the z-table. You can take it from there.
Re: mean and standard deviation
Message posted by Jennifer on January 24, 2001 at 12:00 AM (ET)
Could you please tell me what the relative standard deviation of zero "0" is?
Re: mean and standard deviation
Message posted by miriam (via 62.254.64.6) on February 23, 2002 at 7:29 AM (ET)
hi im having some reeeaaalll problems here.
ive just sat and worked out a million standardd deviations and stuff but now ive come to my write up im not entirely sure what they mean...i know it shows how far away from the mean each score has deviated but what does that say about my results?
HELP!!!!thanks
Re: mean and standard deviation
Message posted by Phil (via 66.32.157.108) on February 23, 2002 at 6:12 PM (ET)
The standard deviation is a relative measure of the "spread" or variation of the data observed around the average. If one sample has a larger standard deviation than another, then it has more variation. I can't tell what you are working on, but the amount of variation can be a very important issue. For example, if you are making parts that are supposed to be a certain diameter, then you want very little variation around the target value.
Re: mean and standard deviation
Message posted by JG (via 128.8.22.35) on February 24, 2002 at 5:50 AM (ET)
Many numerical quantities such as error of measurement have a normal statistical distribution or what we call a 'bell shaped' distribution. This distribution is completly specified by it's mean and standard deviation. However, to do computations we have to transform a general random quantity 'X' to a standard variable 'Z' with mean 0 and SD of 1.
In general there are many interpretations of 'average' besides the mean and many interpretations of variability besides SD. It is customery to use SD as a measure of variability when the mean specifies 'average'.
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