Significant Figures in Calculated Question

Significant Figures in Calculated Question

by James Stewart -
Number of replies: 8

Hey all,

I'm running into a frustrating error with my moodle quiz creation that I am hoping can be corrected. I teach high school chemistry and it is very important that students be able to express answers to the correct number of significant figures. Unfortunately, when I create "calculated" questions (which are the only ones that keep the kids from cheating), it seems to be impossible to set moodle to only accept the answer with the correct sigfigs.

Here are some screen shots to show what I am talking about:

My question: What is the volume of {x} g of ether if the density of ether is {y} g/mL? Give your answer in mL.

 

Here are my setting:

Here is the error I get. As you can see it recognizes the correct answer, but says that it is outside the tolerance range. Problem is, I don't want there to be a tolerance range. I want the students to give me exactly the correct answer to the correct number of sigfigs:

And here is a screen shot of me putting in a correct answer and it being marked wrong. The weird thing is that if I click "fill with correct", it fills it with the answer that I want.

How can I fix this??? It's driving me crazy!

Thanks for your help!

 

-James

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In reply to James Stewart

Re: Significant Figures in Calculated Question

by Pierre Pichet -
James,
You are rigth, the significant figures are not graded directly.
However by setting the error limits, you could control how precise the students should write their responses.
The only way to have exact number format will be to use the short answer to handle the response !!!
Pierre
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In reply to Pierre Pichet

Re: Significant Figures in Calculated Question

by Tim Hunt -
Picture of Core developers Picture of Documentation writers Picture of Particularly helpful Moodlers Picture of Peer reviewers Picture of Plugin developers

You might want to take a look at https://github.com/jamiepratt/moodle-qtype_varnumeric (compatible with Moodle 2.1). That has options for grading response format. That is still only in beta testing, but mostly works.

You may ask why we (the OU) decided to create a completely new question type rather than enhance the existing numerical/calculated questions types? That is a good question. I am not sure I have a good answer. At any rate, it gave us a free hand to try some different things.

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In reply to Tim Hunt

Re: Significant Figures in Calculated Question

by Pierre Pichet -
These are very good news.
As usual Jamie Pratt has done a good job.
These are news that get you happy when you go back to work AFTER holidays smile .
Pierre
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In reply to Pierre Pichet

Re: Significant Figures in Calculated Question

by James Stewart -

I have to say that this is quite disappointing.

The inability to judge whether students express their answers in the correct number of significant digits essentially makes the calculated question type useless for all of the sciences. Just what is the dialog in the beginning where it asks you how many sigfigs the correct answer will have for? What does it do if not grade students on whether they have the answer expressed correctly?

Because of server restrictions I am locked into 1.9 at the momment, so that beta question type that was mentioned for 2.1 would not work for me.

I guess I'll just have to wait for moodle to have the features I (and any teacher of science) need.

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In reply to James Stewart

Re: Significant Figures in Calculated Question

by Pierre Pichet -
Hi James,
Significant figures are just one simple and approximate way to show the possible error in a given number although the real way to do this is the standard deviation.
If you set on your 1,9 Moodle a good response as 3.14 with 0.0001 error, the student needs to give you the exact number you want with the exception that he could add supplementary 0 in the fraction part i.e.
3.14 grade 100%
3.140 or 3.1400 also grade 100%
3.141 could grade 90% if you set the precision to 0.009 for a second answer. This penalty could be seen as for more significant figure than allowed and or less precision than allowed.
3.1 or 3.10 or 3.100 out of range
Although this is not a perfect solution, in most cases the student won't see the differences and even if they do, it will be because they are just lucky as your real value could be 3.141 or even 3.1401.
This solution is only possible if your answers value are in the same decimal range i.e. between 1.01 to 9.99 with the given example.
I already see from the new question code, how to use new available math functions to improve calculated so that it could also handle significant figures.
Pierre
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In reply to Pierre Pichet

Re: Significant Figures in Calculated Question

by Pierre Pichet -
In the next days, I will complete the example by showing how to set the answer to a specific value like 3,14 .
Pierre
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In reply to Pierre Pichet

Re: Significant Figures in Calculated Question

by Pierre Pichet -
The following settings illustrates a way to solve your problem using the round() function.
The {x] and {y} were set so that the good response stays within 50 to 99 with 1 decimal so 3 significant figures.
The response tolerance was set to absolute 0.001 in the first answer and 0.1 in the second answer.
The grade was 100% for the first and 90% for the second
Paramètre {x}
Intervalle des valeurs Minimum - Maximum = 50 -80
Décimales =1  
Paramètre {y}
Intervalle des valeurs Minimum - Maximum = 0.7-0.9
Décimales = 3
round({x}/{y},1)

{x}/{y} round(55.9/0.795,1) = 70.3
Min: 70.299---Max: 70.301
Réponse correcte : 70.3 dans les limites de la valeur réelle 70.3
55.9/0.795 = 70.3
Min: 70.214465408805---Max: 70.414465408805
Réponse correcte : 70.3 dans les limites de la valeur réelle 70.314465408805
Pierre
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