HP 30b: Bug in Student function?
01-04-2015, 04:25 PM
Post: #21
 John Smitherman Member Posts: 81 Joined: Dec 2013
RE: HP 30b: Bug in Student function?
Hi Gerald. For the problem you've stated I used the following key sequence:

5 Input 1.677
Math (shift /)
Probability (down arrow, down arrow, Input)
Student (down arrow, down arrow)

The result is Student 0.923

I hope that helps.

Regards,

John
01-04-2015, 06:10 PM
Post: #22
 Gerald H Senior Member Posts: 1,442 Joined: May 2014
RE: HP 30b: Bug in Student function?
(01-04-2015 04:25 PM)John Smitherman Wrote:  Hi Gerald. For the problem you've stated I used the following key sequence:

5 Input 1.677
Math (shift /)
Probability (down arrow, down arrow, Input)
Student (down arrow, down arrow)

The result is Student 0.923

I hope that helps.

Regards,

John

This indeed gives the correct answer.

Should you then SWAP the two values in the stack & then SWAP them a second time & repeat the calculation the answer is wrong.

Also, if values are recalled & the calculation carrier out in a programme the answer is again wrong.
01-05-2015, 01:51 AM
Post: #23
 John Smitherman Member Posts: 81 Joined: Dec 2013
RE: HP 30b: Bug in Student function?
You're experiencing the vagaries of the HP 30B's stack. This has been discussed several times in this forum. A search should turn up several threads.

John
01-05-2015, 06:28 AM
Post: #24
 Gerald H Senior Member Posts: 1,442 Joined: May 2014
RE: HP 30b: Bug in Student function?
(01-05-2015 01:51 AM)John Smitherman Wrote:  You're experiencing the vagaries of the HP 30B's stack. This has been discussed several times in this forum. A search should turn up several threads.

John

Try a Programme that recalls memory 1 & then memory 2 then calculates ltpt - you will find the answer is wrong. This seems unconnected with "vag¢ries" oft the stack.
01-05-2015, 03:58 PM
Post: #25
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: HP 30b: Bug in Student function?
(01-05-2015 06:28 AM)Gerald H Wrote:
(01-05-2015 01:51 AM)John Smitherman Wrote:  You're experiencing the vagaries of the HP 30B's stack. This has been discussed several times in this forum. A search should turn up several threads.

John

Try a Programme that recalls memory 1 & then memory 2 then calculates ltpt - you will find the answer is wrong. This seems unconnected with "vag¢ries" oft the stack.

@ Tim W.: Isn't that observation something for you to comment?

d:-?
01-06-2015, 02:52 PM
Post: #26
 Gerald H Senior Member Posts: 1,442 Joined: May 2014
RE: HP 30b: Bug in Student function?
To summarise the state of play:

Some say yes, this a bug;

Some are non-commital, saying under certain circumstances the answer is correct & seemingly ignoring the bug question;

Some want others to give opinions;

And yes, the Great Majority are silent.
01-06-2015, 03:15 PM
Post: #27
 Katie Wasserman Super Moderator Posts: 630 Joined: Dec 2013
RE: HP 30b: Bug in Student function?
(01-06-2015 02:52 PM)Gerald H Wrote:  And yes, the Great Majority are silent.

The great majority reading the forum don't use the HP-30b as a 30b but as a WP-34s and may never have even tried the native functions on it before they loaded the replacement firmware.

-katie

01-06-2015, 03:39 PM
Post: #28
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: HP 30b: Bug in Student function?
(01-06-2015 03:15 PM)Katie Wasserman Wrote:  The great majority reading the forum don't use the HP-30b as a 30b but as a WP-34s and may never have even tried the native functions on it before they loaded the replacement firmware.

This great majority makes a statement HP should notice and take into account IMHO.

“The success and prosperity of our company will be assured only if we offer our customers superior products that fill real needs and provide lasting value, and that are supported by a wide variety of useful services, both before and after sales.”

At least the "after sales" customer support seems to be significantly better on the WP side. It's a shame when you remember old HP.

d:-/
01-06-2015, 04:24 PM
Post: #29
 Thomas Radtke Senior Member Posts: 746 Joined: Dec 2013
RE: HP 30b: Bug in Student function?
(01-06-2015 02:52 PM)Gerald H Wrote:  And yes, the Great Majority are silent.
Is this a poll about that bug being a bug? ;-)

Seriously, I think financial models are of interest to only a few members.
01-06-2015, 04:52 PM
Post: #30
 Gerald H Senior Member Posts: 1,442 Joined: May 2014
RE: HP 30b: Bug in Student function?
(01-06-2015 02:52 PM)Gerald H Wrote:  And yes, the Great Majority are silent.
Is this a poll about that bug being a bug? ;-)

Seriously, I think financial models are of interest to only a few members.

No, not a poll.

But, & here I want add weight, so I'll quote Aristotle, "Everyone has an opinion".

Should I apologise for starting a thread about an unworthy financial calculator?

If not here, where?

Still, thanks for opining (implicitly) it is a bug.
Post: #31
 Thomas Radtke Senior Member Posts: 746 Joined: Dec 2013
RE: HP 30b: Bug in Student function?
(01-06-2015 04:52 PM)Gerald H Wrote:  Should I apologise for starting a thread about an unworthy financial calculator?
Sorry, I just tried to explain the silence. Of course, the 30b is on-topic in this forum.

[Edited to replace 20b for 30b]
02-15-2016, 12:19 AM
Post: #32
 lrdheat Senior Member Posts: 560 Joined: Feb 2014
RE: HP 30b: Bug in Student function?
I checked this on the Prime...the HP 30b, when the = or other keystroke is entered is allowing (as with the Prime), decimal degrees of freedom, and is calculating cum from 0 to 1.677 for 1.677 degrees of freedom (to arrive at .8706... ). Why it does so is odd?
02-15-2016, 12:35 AM
Post: #33
 lrdheat Senior Member Posts: 560 Joined: Feb 2014
RE: HP 30b: Bug in Student function?
Correction....cum from -infinity to 1.677.
02-15-2016, 06:56 AM
Post: #34
 Dieter Senior Member Posts: 2,397 Joined: Dec 2013
RE: HP 30b: Bug in Student function?
(02-15-2016 12:19 AM)lrdheat Wrote:  I checked this on the Prime...the HP 30b, when the = or other keystroke is entered is allowing (as with the Prime), decimal degrees of freedom, and is calculating cum from 0 to 1.677 for 1.677 degrees of freedom (to arrive at .8706... ). Why it does so is odd?

What exactly is odd here? Non-integer degrees of freedom can be handled easily as the Student CDF can be expressed by the Incomplete Beta function. The 34s also returns 0,8706432972715508 here.

Dieter
02-15-2016, 02:57 PM
Post: #35
 lrdheat Senior Member Posts: 560 Joined: Feb 2014
RE: HP 30b: Bug in Student function?
Odd referring to why the 30b is using 1.677 for X and n when a key such as = is pressed before going into the menu tree to find the answer in the example...
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