# [LON-CAPA-users] Puzzling situation...

Stuart Raeburn raeburn at msu.edu
Fri Feb 22 14:23:28 EST 2013

```Hi,

> Any ideas anyone on why in the second instance (\$db12, id=25) 0 is
> accepted as a correct answer but in the other instance (\$dy11,
> id=22), 0 is returned as incorrect???

Perhaps you are seeing an artifact of floating point calculations in
the situation where the answer is zero, and you are using a relative
tolerance?

Stuart Raeburn

Quoting "Mills, Douglas G" <dmills at illinois.edu>:

> HI All,
>
> We're greatly perplexed by this situation.  We have a student whose
> results for two different responses in a part should be 0, but the
> answer is accepted for one of the responses and not accepted for the
>  other. To the best of my abilities to discern, everything about the
>  two items is identical (and having written these, it's almost
> certain that I cut and pasted my way from one to the other) and the
> data for the two are analogous.
>
> The formulas for computing the two answers are:
>
> \$dY11=&format(\$EAY11-\$AY11,"2s");
> \$dB12=&format(\$EAB12-\$AB12,"2s");
>
> The values for the variables in her instance are:
>
> \$EAY11=4.2e-1
>
> \$AY11=.42
>
> \$EAB12=2.6e-1
>
> \$AB12=.26
>
> The coding in the problems looks (is!?) identical as well:
>
> <responseparam name="tol" type="tolerance" default="2%"
> description="Numerical Tolerance" />
> <responseparam name="sig" type="int_range" default="1,2"
> description="Significant Digits" />
> <textline /> \$PART20msg[1]
> </numericalresponse>
>
> <responseparam name="tol" type="tolerance" default="2%"
> description="Numerical Tolerance" />
> <responseparam name="sig" type="int_range" default="1,2"
> description="Significant Digits" />
> <textline /> \$PART20msg[4]
> </numericalresponse>
>
> Any ideas anyone on why in the second instance (\$db12, id=25) 0 is
> accepted as a correct answer but in the other instance (\$dy11,
> id=22), 0 is returned as incorrect???
>
> Doug
>
> Douglas Mills
> Director of Instructional Technologies
> Department of Chemistry
> University of Illinois
> dmills at illinois.edu<mailto:dmills at illinois.edu>
> (217) 244-5739
>

```