marking of calculated questions

marking of calculated questions

by Beng Pu Siang -
Number of replies: 4

THis questions contain 3 screen shots....

I set a few calculated questions wanting students to give the answer to 3 significant figures to I set it as follows....

 2.JPG

But when I attempt the questions, I get the following

1.JPG

THe setting screen is as follows

3.JPG

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In reply to Beng Pu Siang

Re: marking of calculated questions

by Pierre Pichet -
Thanks for the post, I will do some tests and come back later.
Which moodle version are you using?

Pierre

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In reply to Beng Pu Siang

Re: marking of calculated questions

by Pierre Pichet -
I have created a bug MDL-11860 on this problem which is related to the rounding limits.
I have tested it with 34013 but also with 30000 and 40000. In the last two values everything goes well
However you can get a work-around if you set {a} to be between say min 200 and max 400 and you write your question this way
{a}00 cm =___km
and change the formula
{a}/1000
I have tested it.
You should also correlate your tolerance limits to more reflect the values you accept. If you stay in the 10000-90000 cm your answers will be between 0,100 and 0,900 so your tolerance limits should be 0.001 nominal. In this case everything is OK.
I have tested it.
So this is less a bug than a good knowledge of the interactions between the tolerance and the rounding. At least it should be more documented ...

Pierre

P.S. the 13 in 34013 creates conflict between the rounding process (number of decimals) and the grading limits .

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In reply to Pierre Pichet

Re: marking of calculated questions

by Beng Pu Siang -

My initial intention was to test on the appreciation of rounding off... Seems that the method you gave will not give the student a chance to practice rounding off.

But if that is what can be offered. I will do a work around until there is a solution.

THanks for the effort

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In reply to Beng Pu Siang

Re: marking of calculated questions

by Pierre Pichet -
This (rounding) is not correctly fixed in moodle because of the handling of real numbers by PHP. Sometimes the internal representation of real numbers as power of 2 (computers work with binary representation not decimal) have the consequence that 4.000000/2.0000000 does not necessarily give 2.000. You obtain something like 1.999999992 or 2.0000001.
To be on the student side, the responses are tested with an increment (set following the precision level of the PHP installation) so that the 2.0000001 is accepted as 2.00000 and -1.999999992 as -2.00000.
The actual grading has no mean to test the rounding or the significant figures. It just control the display of the good answer. However the future multichoice option will let you create responses where you could test the students on significant figures or precision.

Pierre




P.S. Different PHP math lib libraries can be installed on moodle which complicate finding an universal solution.

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