Regresson Analysis for Net promoter Score (NPS)

Issue: I am trying to calculate with Excel a regression Analysis for NPS scores but outcome, I am sure is not right. Not sure I am using the right Valirable.

Background: The Net Promoter Score(NPS) is an index ranging from -100 to 100 that measures the willingness of customers to recommend a company's products or services to others. “On a scale of 0 to 10, how likely are you to recommend this company’s product or service to a friend or a colleague?” Based on their rating, customers are then classified in 3 categories: detractors, passives and promoters, and NPS is calculated.

What I am doing: Using the scale of 0 to 10 as a dependent variable. Using time a service lasts (In days). When I use Excel scatter plot to see the dispersion of the dots, basically, it represents 10 lines of dots from X axis. (I think I am doing something wrong):

Any idea what would be happening? Am I using the wrong dependent variable?

Thanks!

I am not sure what you mean by "Using time a service lasts (In days)."

Regression analysis attempts to fit the various predictor and explanatory variables in the equation, y=f(x), where f(x) is a function of x's(independent/explanatory variables) and y is the predictor/dependent variable.

If you are trying to run NPS scores against time, you need to consider time when NPS is calculated/captured along with NPS score.

So in that case, column with NPS values would be independent variable(to be put in X range in Excel). And the column with "time" would be dependent variable(to be put in Y range in Excel)