Is there a way to give partial credit for answers in a multiple choice test?

Is this needed as a question in a post-course test to be tracked by SCORM as part of the test score? If so, there really isn't a way to do it. You can change the weighting of a question as a whole but not the value for any specific responses. You can have partial scoring on or off, set in the Publishing Profile or as a question setting, but the value for partial scoring is based on the correct/incorrect responses and what the learner selects. 

What you're pretty much describing is a Lichert-type question, which we've never created as a formal question type since it's mostly used for surveys and most LMSs have built-in survey tools with reporting.  

If it doesn't need to be a in a post test, though, you could create a page that has a Radio Button element (from the Insert tab select Inouts then choose one of the two Radio Buttons options there). This adds a three-item radio button list (you can add more if needed) that is set up like a Lichert question that you can use to set a variable. Or you could use a Slider for the learner to drag to indicate their rating, which could set the variable. Or have five buttons on a page and each sets a variable to a different value when selected. (This last option is probably the best if you need more customized values for the choices, the first two ptions will set the values from 1-5, for example.) You could have as many of these pages as needed, each setting a different variable. 

No matter how the variables are set, the value would be stored for the course duration and you could show it to the learner on the same page or any page after it's been set. It will allso be sent to the LMS if the learner closes the courses out, and gets passed back to the course when they re-launch the course later. 

If you need to generate reports on this, the variavle can be sent as xAPI statements to an LRS for tracking/reporting.

Those are the options I can think of for now. Let us know if these are helpful or if there are other aspects fo what you're looking to solve that we should know about.