The Museum of HP Calculators

HP Forum Archive 14

 To Karl, StatisticsMessage #1 Posted by bill platt on 24 June 2004, 11:13 a.m. Quote: [SNIP from an old post, regarding the 2-variable statistics handling of voyagers, vs the pioneers and the 67] Technically, it's not a bug, per se -- the 15C performs its 1- and 2-variable statistical and regression functions as they are designed and documented. The real problem is automatic summation and calculation of y-variable stat data even when the user deliberately enters only x-variable data. Glitches caused by GIGO sometimes happen, if the user is not careful, or doesn't know how to fix the errors. Unfortunately, this functionality on HP's RPN calc's leaves much to be desired, for a number of reasons. More about this later. Happy Thanksgiving! Karl, have you handled the "more about this later" yet? best regards, Bill

 HP RPN's : deficiencies in stat summationMessage #2 Posted by Karl Schneider on 25 June 2004, 1:07 a.m.,in response to message #1 by bill platt Hi, Bill -- Wow! That's dredging the archives. Yep, I wrote that, so here's the "short essay" I had in mind: The usability of statistical-summation functions on RPN HP calc's (not including the RPL HP-28/48/49 and the algebraic-based 27S/17B/17BII) falls a bit short, in my estimation. This basic functionality was implemented more sensibly and thoughtfully even in older Casio and low-end TI calc's, as I see it. On many HP RPN calculators: 1. Entering 2-variable data pairs puts the values in reverse order. This can be overcome on the RPN models by entering the values in reverse order, or with x<->y before SIGMA_+, but this is annoying. On algebraic models by HP and others, x INPUT y SIGMA_+ maintains the order of the data pair. 2. 2-variable summation and calculation of standard deviation (SD) are automatically performed, even when unnecessary. This sometimes causes problems, if "leftover" value(s) are used for y-summation in 1-variable analysis, then SD is calculated. The "debris data" might cause a sqrt(neg) error when the SD function tries to calculate both x_SD and y_SD. Erroneous y-summation registers must be cleared before the x_SD answers can be obtained. The 32S/32SII get around this by providing separate commands for x_SD and y_SD. The Casio and TI models typically have separate user-selected modes for 1-variable and 2-variable analyses. 3. The ability to specify repeated data or data-pairs is not provided. By contrast, TI offers "FREQ" for entering repeated data. Casio calc's offer a similar capability. 4. Sample SD's, rather than population SD's, are calculated. I never quite understood HP's emphasis on sample SD's. I would think that the most common applications for basic stat on a calculator would be a teacher computing mean and SD for class scores, or a student doing the same for laboratory observations. For either of these cases, the population SD would certainly be appropriate. It is no more difficult to obtain a sample SD by first subtracting the mean as a datum, as to obtain a population SD by first adding the mean. Again, the 32S/32SII/33S offer both population and sample SD's. Menus made this choice easier to provide. There are other gripes, many of which pertain only to certain models. For instance: The HP-41 didn't even have 2-variable stat built in (it could be added with a Stat Pac). The 34C/11C/15C omit certain useful functions (e.g., x-estimate) and kluge others together as one function (y-estimate and coefficient of regression). This situation probably stemmed from lack of sufficient available keyboard space. Much of this is "water under the bridge", but I view this as one instance of something that HP didn't implement as well as its competitors. -- Karl S. Edited: 25 June 2004, 1:14 a.m.

 Re: HP RPN's : deficiencies in stat summationMessage #3 Posted by Raul Lion on 25 June 2004, 2:15 a.m.,in response to message #2 by Karl Schneider Quote:The HP-41 didn't even have 2-variable stat built in (it could be added with a Stat Pac). Yes, it has MEAN and SDEV, Karl, but neither LR nor curve fitting (they could be added with Advantage pac)

 HP-41 statistical functionsMessage #4 Posted by Karl Schneider on 26 June 2004, 1:29 a.m.,in response to message #3 by Raul Lion Hello, Raul -- Yes, you are correct -- the HP-41 models do indeed have 2-variable summation built-in. My hastily-written "2-variable stat" was intended to mean "regression analysis", of which the HP-41 models have no built-in capability. The Stat Pac preceded the Advantage Pac in offering regression-analysis routines (linear, logarithmic, exponential, and power). It seems silly to have built-in 2-variable summation without the functions to utilize them. Maybe it was a gambit to sell Stat Pacs...

 Re: HP-41 statistical functionsMessage #5 Posted by Raul Lion on 26 June 2004, 2:49 a.m.,in response to message #4 by Karl Schneider Quote:It seems silly to have built-in 2-variable summation without the functions to utilize them Yes, Karl. And it seems more silly, sell CFIT programs that build the summations in other way...so the buit in MEAN and SDEV are useless with the data stored with those CFIT...

 Re: HP RPN's : deficiencies in stat summationMessage #6 Posted by bill platt (les Estats Unis d'Amerique) on 25 June 2004, 11:01 a.m.,in response to message #2 by Karl Schneider Hi Karl, Quote: Wow! That's dredging the archives. Yep, I wrote that, so here's... Yes, you nevr know what interesting stuff you will find when you go searching for one of Valentin's old hp-15c Challenges... Your description is useful from a practical standpoint, but aso from a design and appreciation standpoint: if one never ventures outside of the HP world, it is really not possible to judge fully the genius and quality of the classic hp products. Nothing is truly perfect in this world. Best regards, Bill

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