How to add a rating scale with different weights

OK, I see. Then assuming the fields are named Q1 to Q8 you can use this code as the custom calculation script of the total field (formatted as Percentage) to show the result:

var questionsData = [
	{name: "Q1", rating: 0.15},
	{name: "Q2", rating: 0.15},
	{name: "Q3", rating: 0.15},
	{name: "Q4", rating: 0.15},
	{name: "Q5", rating: 0.15},
	{name: "Q6", rating: 0.05},
	{name: "Q7", rating: 0.15},
	{name: "Q8", rating: 0.05},
]

var total = 0;
for (var i in questionsData) {
	var f = this.getField(questionsData[i].name);
	total+=(Number(f.valueAsString)/5 * questionsData[i].rating);
}
event.value = rating;

Edit: Code fixed thanks to Nesa