Bar Chart of student performance - Tableau

Question

I have this dashboard. In sheet two , the bar chart is just counting the number of marks in each range specified in the x-axis. What I actually want is a bar chart according to the same range, but it should count the average of marks of each student. In sheet 3, the bar chart looks similar to what I expect, but if you take a look, it's just adding each average of student one above the another.

So, how can I make a char bart with frequency of students average of marks. The ranges should be: [0 , 5>,[5,10>, [10,15>, [15,20].

Answer 1

One solution is to create a custom SQL data connection to first calculated the avg NOTA for each student as below:

select NOMBRES, avg(NOTA) as avg_nota from YOUR_TABLE group by NOMBRES

Then you can create a histogram for avg_nota, either with Show Me or manually.

Here is a link to an example based on your original

The SQL above weighs each score equally, which is fine if each course has exactly the same number of grades. But if the number of records varies between courses, you should adjust the approach to make sure each course is weighted the same (e.g. so that a course with 10 small tests does not get weighted twice as much as a course with 5 larger tests). The solution in that case, might involve repeating the above step in a nested subquery or view grouping by both NOMBRE and CURSO. Still this simple approach should give you the basic idea.

The solution above works but I think there ought to be a way to get the same effect using table calculations without resorting to custom SQL