$\begingroup$

The part of this question that raises red flags for me is the line:

However, many timesit [sic] is good to have a wide spread of grades.

Why? This seems backward reasoning to me wherein you know the distribution of grades that you want to give and are figuring out how to design the test to fit that distribution.

Your assessment should be criterion based. Look at your learning objectives for the course and design the assessment accordingly. For example, here is my scheme of work for one course. Note in the introduction how the skills are knit to the grades.

In designing the exam, the question that I have always before me is:

"What competence can I use this question as evidence for?"

I also imagine the following scenario. Suppose that a year later, another lecturer storms in to my office and demands to know why I gave a particular student a particular grade. What will I answer? That they scored 52 points? That they hit a particular number of standard deviations away from the mean? Or that in their exam then they demonstrated that they met the criteria for the given grade?

So when I have complete freedom to set the exam and the assessment criteria, then I design my exam by these principles. Each indecomposable unit on the test will be used as evidence for their grade, but each such unit comes with a maximum grade that it can be used for. So when assessing for an E, I ask "Has this student shown sufficient evidence that they deserve an E?" meaning that I count the number of answers rated "E" or above. If this is sufficient, they have secured an E. Next, I look at the "C" grade. Any answers rated only E are now dropped. Note that some answers could only get an E so these are automatically dropped. I do the same at the "A" grade. For "B" and "D", I take these to mean "almost the grade above". So a "B" is a "low A", not a "high C".

As an example, here's an exam designed on these principles. I don't say that it is perfect. Note the first question only asks about definitions and statements. So the answers to this question can only count for an E, but I give them lots of opportunities to show that they have achieved that level. The other questions basically allow for Cs and As (one part of each question can be given an A, I'll leave it as an exercise to work out which part).

In short, if you are worrying about the distribution of grades then you are worrying about the wrong thing. If you are worrying that the grades are not knit to the desired competencies of the course, then you are worrying about the right thing and the solution is obvious: test for the desired competencies, not for anything else. And never grade by just adding up points.