title: Exponentially weighted moving average- without mean or standard deviation?
body: <p>Hi I have collected some process data for 3 years and I want to mimic a EWMA prospective analysis, to see if my set  smoothing parameter would have detect all the important changes (without too many false alarms).</p>
  
  <p>It seems like most textbooks and literature that I have looked that use a mean and standard deviation to calculate the Control Limits. This is usually the "in-control" mean and standard deviation from some historical data, or the mean and sd of the population from which the samples are drawn. I don't have either information.</p>
  
  <p>Is there another way to calculate the Control Limits?</p>
  
  <p>Is there a variation of the EWMA chart that does not use mean and standard deviation?</p>
  
  <p>Any creative ideas?</p>
  
  <p>Thank you in advance</p>