Can I have a reveal button at the bottom of my form which will reveal an extra row on my matrix?

Hi,

So basically I want to produce a matrix with yes/no check boxes as a type of test.

Would I be able to add a reveal button that reveals an extra coloumn with the correct answers?

any advice would be useful

To clarify, would you like to have a button that will reveal the answer while the user is still filling out the form? That would give them the answers freely? We do not have a specific function that allows you to have a separate column with a button that displays the correct answer.

However, if you would like to provide the correct answers to your users after they submit the form, then you can use the Quiz Form app. Here's a link to it: https://apps.jotform.com/app/quiz_form. That should allow you to provide the correct answers to your users via email or by posting it in your "Thank You" page. 

Now another concern that I have is the input type for the matrix, you have chosen to use the "Check box", but that allows your users to select multiple items for each row. Here's how it looks like:

It's true that the instruction says that they should only mark "1" box, but there's no validation or restriction that will prevent them from selecting two check boxes. 

I would suggest using the "Radio button" input type if you require your users to answer all the questions and select only one option per item.

This is how it looks like when you user the "Radio Button" as the input type:

Aside form that, you can also assign calculation values on your fields and use the Form Calculation widget or the Conditional Logic feature to calculate your own custom scores.

I hope that helps. Let us know if you need further assistance on this.