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Old 07-31-2007   #1
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Default Probability in Excel?

I've been trying to do problems like this in Excel. I use the "NORMSDIST" function, but the answers I insert into my online homework program don't register them as correct. Just wondering if I'm using the right function or what I'm doing wrong. I just plug in the value that they want in the problem and use the answer as I get as the probability. I thought maybe I was supposed to use z-score, but that didn't work either.Assume that the readings on the thermometers are normally distributed with a mean of 0(degrees) and a standard deviation of 1.00(degrees). A thermometer is randomly selected and tested. Find the probability of each reading in degrees. (a) Between 0 and 1.57: (I got 0.941792444)(b) Between -2.61 and 0: (c) Between -0.98 and 2.66: (b) Less than -1.71: (c) Greater than -1.45:
Old 07-31-2007   #2
trying hard
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huh? next question pls.
Old 07-31-2007   #3
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I think NORMSDIST is the right function, but you may be misinterpreting the results. Remember that NORMSDIST is returning the value of the cumulative density function, which is the probability that the reading will be somewhere between +z and -z. But what you want to know is, what is the probability of the reading being between:a) 0 and zb) -z and 0etc.I'll tell you how to do the first one and you should be able to take it from there: the probability of it being between 0 and 1.57 is exactly half the probability of it being between -1.57 and +1.57. So in Excel that would be,=NORMSDIST(1.57) / 2You should be able to get them all now, but will have to think a little more to get (c). Hint: treat the range of (c) as two separate problems.Good luck!

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