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Subject: [office-formula] problems with some functions, most statistical

• From: Regina Henschel <rb.henschel@t-online.de>
• To: office-comment@lists.oasis-open.org
• Date: Sat, 08 Nov 2008 21:27:20 +0100

```Dear members,

working on the statistical functions in OpenOffice.org I have come
across some problems in the draft specification
Some of them are only editorial remarks, but others are really essential.

It would be nice if a mathematical expert in your group could have a
look at the problems and gave me feedback.

Best regards
Regina Henschel

I miss the factor 1/(b-a) in the density case, see
http://www.itl.nist.gov/div898/handbook/eda/section3/eda366h.htm

== 6.15.33 GAMMA ==

There is the constrain N>=0 set, but GAMMA(0) is not defined. Therefore
it should be at least N>0. But usually the Gamma-function is defined for
all real numbers with exception of zero and negative integers. So the
constraint should be: N<>0 and N not a negative integer.

== 6.15.35 GCD ==

"Return the largest value that can be evenly divided (no remainder) into
the given numbers." should be "Return the largest value that can divide
the given numbers evenly (no remainder)."

== 6.17.37 INTERCEPT ==

Only some editorial remarks to the text "Calculates the point at which a
line will intersect the y-values by using known x-values and y-values."
1. It calculates no point but a single value. 2. The line does not
intersect the y-values but the y-axis. 3. It does not say, that the line
is the linear regression of the known values.

== 6.17.53 LEGACY.NORMSDIST ==

The text "This is exactly NORMDIST(x)." should be "This is exactly
NORMDIST(x;0;1)." because mean parameter and standard deviation
parameter are not optional.

== 6.17.60 PHI ==

The description is not as clear as possible. PHI is the density function
of the standard normal distribution, therefore
PHI(x)=NORMDIST(x;0;1;FALSE()).

== 6.17.63 QUARTILE ==

The example calculates with Quart=1.5 although there is a constraint
INT(Quart)=Quart

== 6.17.64 RANK ==

The description "If not 0, Data is ranked in descending order." has to
be "If not 0, Data is ranked in ascending order."

== 6.17.71 STDEVA ==

The text "cells with text are converted to 0;" conflicts with "The
handling of strings is implementation defined."

== 6.17.76 TDIST ==

The formula shows the density function, but TDIST actually calculates
the cumulative distribution function in OOo, Excel and Gnumeric.

== 6.17.79 TRIMMEAN ==

The limits in the definition formula are wrong. Either count the data
from 0, then sum from i=cutOff to n−1−cutOff; or count the data from 1,
then sum from i=cutOff+1 to n−cutOff.

== 6.17.80 TTEST ==

A lot of problems :(
(1) All formulas miss the degrees of freedom. It is necessary for TDIST.
In case unequal variance there must be defined, whether the degrees of
freedom are made integer by FLOOR or whether they remain real.
(2) In case paired: sqrt {n-1} is wrong because it is already contained
in s_{X_1 - X_2}.
(3) In case equal variance: definition of s² is missing.
(4) In case unequal variance: definition does not meet usual
definitions. In fact it is the definition for the equal variance case,
with pooled variance.
(5) As TDIST actually returns the values of the cumulative distribution
function, the definite integral in the formulas has to be revised
together with TDIST.

== 6.17.85 WEIBULL ==

Alpha and Beta are exchanged in the formula, compared with the current
implementation in OOo, Excel and Gnumeric.

== 6.17.86 ZTEST ==

The draft specification defines the result as 1-P(-|z| <= Z <= |z|),
which is a two-tailed form. But the current implementations use a
one-tailed form. Besides a real bug in OOo, Excel and OOo return
1-P( Z<=z) for z>=0 and
P( Z <= |z|) for z<0
Gnumeric returns P( Z <= |z|) for z<0 too, but I do not understand the
result in Gnumeric for z>=0.

In other cases of changed semantic, for example the change from right
tail to left tail in CHIDIST, for the old version LEGACY was introduced.
Shouldn't there be a differentiation in the case of ZTEST too? I know
the specification is only about the internal names and using a prefixed
name for the old version internally is possible. But the names in the
specification give a strong hint how the functions should be named in
the UI of the applications and unique names in different applications
would make working with different applications much easier for users.
```

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