What does "Right numerical value, wrong units" really mean (to you)

What does "Right numerical value, wrong units" really mean (to you)

autor Tim Hunt -
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This is in relation to the numerical question type.

Since Moodle 2.0, you can have it so that the student gets partial credit if they answer with the right numerical value, but with the wrong unit.

That sounds so simple doesn't it? Sadly it isn't to start to get a glimmering of the type of problem that is possible, here is a slightly artificial example:

Question: "A circle has a radius of 0.00005km, what is its area? (remember to give the correct unit)"
Accepted units: cm2 or m2

What answers would you consider to be "Right numerical value, wrong units" and why?

If you wish to cheat, you can read the discussions in MDL-27418 and MDL-28118, but it would be more useful (I think) if you try to answer before you read that.

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Re: What does "Right numerical value, wrong units" really mean (to you)

autor Jean-Michel Védrine -

I think this is an example of a "nearly non sense expression" : such a problem has only a right response made of a numerical value AND a unit.

In fact if a student give me a number like 12.3456789 I can't say if it's right or wrong because we can always imagine an "unit"  EZSSDRE from planet HHJGFHKJH for wich this numerical response might be right zubit se

So the only meaning I can give to "Right numerical value wrong unit" is in the case the student did give a numerical value AND unit wich form a correct response but the unit wasn't allowed in my question.

In your question this would be the case if he give me the right response but in km2 or mm2 or ...

PS1 I can promise that have not read MDL-27418 or MDL-28188, I did visited these pages a few days ago, but as says one my students one day "There were too many lines for you to expect that I would read that kulit oči !"

PS2 I am sure antybody has worked that 1 EZSSDRE is 6,36172518 cm2 unless I made a mistake (wich happend to me quite more frequently than you could imagine for a math teacher červenání )

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Re: What does "Right numerical value, wrong units" really mean (to you)

autor Joseph Rézeau -
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I'm far from being a mathematician, but I totally agree with Jean-Michel that the only answer to that kind of question that makes sense is one which would include a numerical value AND a unit.

Furthermore, it would seem logical to me that the unit that is set in the question should also be the one used in the answer, i.e. km -> km².

Joseph

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Re: What does "Right numerical value, wrong units" really mean (to you)

autor Pierre Pichet -
Hi Joseph, As this is not part of the main discussion, using a different unit in the question is one way to control if the student can convert 0,00005 km to a cm or m value before doing the calculation.
This is one of the "compétence" that we need to control although a simple question without the calculation will more readily test this "compétence".
However such a multiple step question reflects more real life as complete sentences in your regexp questions. úsměv
Pierre
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Re: What does "Right numerical value, wrong units" really mean (to you)

autor Derek Chirnside -

I'm a Physicist if I am anything.  It's clear to me:

Assume the numerical answer is 24

  1. you don't say a 'speed of 24 Joules'.  It's km/hr (etc) =penalise unit.  Common problem in physics: right answer, wrong unit.
  2. "24 mm2" when the answer is "24 m2" =penalise unit
  3. 24 EZSSDRE.  Hmm.  If it's something I can look up (like a cubit from Noah) then you have a problem, it could be right answer in that unit.  Solve by saying "Use Metric system units"  Then your only problem is allowing for m2, km2, mm2 as all different options in your automated question answers.

NZ practice in handwritten National exams for Physics: penalise up to X times for wrong unit then ignore it.  X~3-5

But of course I have not looked at the questions.  Just thinking how I'd expect it to work.  I think Jean-pmichael is right.

-Derek

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Re: What does "Right numerical value, wrong units" really mean (to you)

autor Pierre Pichet -
Tim,
Thanks to start the discussion this way, moodle being a community.
The question can be simplified to just asking
Express the value of 0,00005 km in cm or in m, give the unit.
Pierre
P.S. I don't want to give any cue, but trying to create such a question in moodle 2,0 (i.e. Moodle Demo site) and 2,1 site should illustrate the dilemna.
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Re: What does "Right numerical value, wrong units" really mean (to you)

autor Pierre Pichet -
I think that the following version of question illustrates more precisely the problem.
You are giving a test which is time controlled and the question
"Express the value of 0,00005km in cm or in m, give the unit."
is the last one.
You are grading the question as 100% for the numerical value and you apply a penalty of 20% if the unit is not the correct one or badly written or not given.
Student - response

A 5 cm
B 5 m
C 0,05 m
D 0,05 cm
E 5 c
F 0,05
E 5
To which student(s) will you give a 100% grade, a 80% grade, a 0% grade ?
Pierre
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