A question on STACK for K8 Math

A question on STACK for K8 Math

by yew hong ng -
Number of replies: 3

Hi I do not currently have a moodle set up but am trying to understand whether Moodle (with STACK, perhaps) can do what I want.

I've gone through the demo quizzes for STACK. They do not include examples of what I need.

Basically, because I teach lower level Math (middle school), the Algebra we do does NOT like too many multiple answers. For example, a question may be:

Factorize the quadratic expression $$x^2-2x+1$$.

I will only want answers like $$(x-1)^2$$ or $$(1-x)^2$$. I wouldnt want to accept $$x^2-2x+1$$ or $$1-2x+x^2$$.

Is this kind of questions possible with STACK. If not STACK, any other moodle plugin?
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In reply to yew hong ng

Re: A question on STACK for K8 Math

by Tim Hunt -
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Right, this is a key issue: what properties of the answer do you care about when grading?

STACK has an answer to this. When you create the question, and tell Moodle how you want the response graded, you do it by applying a number of different 'answer tests' to check the properties that you care about.

For example, you might apply two tests:

  1. The student's answer is algebraicly equivalent to $$x^2+2x+1$$; and
  2. The student's answer is fully factored.

Alternatively, you might use the STACK answer test 'equal up to commutivitiy and associativity' (but I'm not sure if that copes with the minus sign here). I just checked. No it does not, so you would have to do somethign like

  1. The student's answer is equal up to commutivitiy and associativity to $$(x-1)^2$$; or
  2. The student's answer is equal up to commutivitiy and associativity to $$(1-x)^2$$.

Basically you have a lot of control of exactly what you want to grade right or wrong, but you do have to learn how to do that. Fortunately, Chris's documentation is pretty good.

See https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/Authoring/Answer_tests.md and https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/Authoring/Authoring_quick_start.md
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In reply to Tim Hunt

Re: A question on STACK for K8 Math

by yew hong ng -

Thanks. I'm excited. I hope my school It administrator can get it set up correctly.

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In reply to Tim Hunt

Re: A question on STACK for K8 Math

by Christopher Sangwin -
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Thanks Tim,

For this example you might also like to look at the "factored form" test.  This test is designed to establish if the answer is in factored form and equivalent to the teacher's answer. This test *does* cope with even powers and minus signs under the bracket.  It also provides useful feedback for answers like (4*x-8)^2

If you come across other elementary things like this and can't work out how to establish the properties please ask. I'm likely to have already written questions which cover it. In particular, the Demo course distributed with STACK has representative questions covering all the manipulations in http://www.mth.kcl.ac.uk/staff/ad_barnard/Pocket.pdf  Tony's "map" is used as a catalog for the questions so you can find them.

Chris

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