Puzzling HP-49G+ SDEV-function Message #1 Posted by Karl-Ludwig Butte on 26 Mar 2006, 7:03 a.m.
Hello All,
I have a difficult question about the SDEV function of the HP-49G+ which puzzles me: There are 4 figures for which I would like to calculate the standard deviation:
6.5
12.1
5.4
-10.3
I've read this excercise in a financial mathematic text book and the author is calculating the standard deviation as follows:
SDEV = SQRT(1/4*(SQR(6.5-3.4)+SQR(12.1-3.4)+SQR(5.4-3.4)+SQR(-10.3-3.4))
SDEV = 8.3
When entered into the HP-49G+ and using the formula above the same result is displayed. But using the predefined function Mean and SDEV the 49 displays:
Mean: 3.4250
SDEV: 9.6088
First I thought it maybe because in the textbook the 3rd and 4th decimal isn't used so I recalculated with 3.4250 instead of 3.4 but in vain. Tries with an HP-49G, HP-48G and HP-41 the same differences in results were displayed. So it doesn't seem to be a bug of the HP-49G+ Firmware (Version: HP49-B Rev.: 2.01-2).
Has anyone of you a hint where the difference comes from ? Thank you very much in advance.
Has anyone
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