HP 17bII+ stats bug



#2

(I originally posted this to comp.sys.hp48... with 2 ppl confirming that this is a bug, user beware... just glad i didn't find this while taking a test or something!)

----------------------------------------

This many simply be a misunderstanding of how the calculator works, but if you have one, can you please try the following? (I am using RPN mode)

Create a list "X", 5 items:
10
15
20
25
30

Create a list "Y", 5 items:
1003
1005
1010
1011
1014

Do stat calculations on the lists. CALC->MORE->FRCST

X Variable is "X"
Y Variable is "Y"

Switch to LINEAR mode (MODL->LIN)

In the FRCST menu press "MORE" until you see the sumX, sumY, sumX2, sumY2... menu (Don't press CORR, M, or B at any point during this time)

Verify:
sumX = 100
sumY = 5,043
sumX2 = 2,250
sumY2 = 5,086,451
sumXY = 101,000

Now, press "MORE" until you get to the "X Y CORR M B" menu. Press "CORR" to calculate the correlation value. The value displayed should be 0.9826...

Now, press "MORE" until you are back at the summation screen. See if the summation values show the following:

sumX = 100
sumY = 5,043
sumX2 = 250
sumY2 = 81.20
sumXY = 140

Why did the last 3 sums change??? The same seems to happen if you choose M or B instead of CORR. The only way to get 101,000 for sumXY is to exit the FRCST menu completely and rechoosing the X Y lists again...

Pilot error or bug???


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