I have daily surveys sent to users of several of my organization´s services, the surveys consists only on NPS question (How likely would recommend X? on a 0 to 10 scale), number of respondents vary by day and service.
I would like to get the NPS score and confidence interval for a service on a monthly scale. Is it ok to joust aggregate the data points and calculate CI as in a cross-sectional survey?
After calculating monthly NPS I would like to compare scores from different services. Wold this be a valid approach?
Supposing the number of respondents is equal or grater than the number of respondents required in a cross-sectional approach. Is this a valid way to obtain a representative sample of the users of such services over a month?
Finally I would like to compare the NPS of a service before and after some significant project is made to improve the service. Projects usually take a few months to implement and have a marked go-live date. Wold comparing the NPS of months after the improvement to the NPS before the improvement be valid?
Thanks for your advice.