Is forecasting and predictions part of Inferential or Descriptive? Can someone please explain to me which statistics forecasting and predictions are part of? Inferential or Descriptive? I am working on an homework. I was unable to come across the answer in my reading.
 A: From What are descriptive and inferential statistics?:

  
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*Descriptive statistics provide a concise summary of data. 
  
*Inferential statistics use a random sample of data taken from a population to describe and make inferences about the population
  

I would say predictions and forecasting use both, depending in the level of knowledge you have. You forecast or predict outside your known data. To do that, you often use descriptive statistics to summarize your data to a line, for instance, and then extrapolate. 
However, if you have to choose one, inferential is generally the most appropriate. You can look at Descriptive, Predictive, and Prescriptive Analytics Explained, with an additional term, prescriptive:

  
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*Descriptive Analytics: insight into the past
  
*Predictive Analytics: understanding the future
  
*Prescriptive Analytics: advise on possible outcomes
  

However, "predictive" can be understood for interpolation too. For a more solid reading, I suggest: To Explain or to Predict? Galit Shmueli, 2010, Statistical Science:

The purpose of this article is to clarify the distinction between
  explanatory and predictive modeling, to discuss its sources, and to
  reveal the practical implications of the distinction to each step in
  the modeling process

A: At first blush a forecast could be considered inferential as it infers the future but upon reflection the mean of a series is clearly descriptive and could be the basis of a forecast. If this is so then the mean is both descriptive and a forecast. An ARIMA model more generally describes a series (not uniquely) and is also usable to make a forecast. Thus the forecast can be considered descriptive given the model.
Clearly the person who down-voted this is a statistical novice as no reason was given. That is a shame as we can all learn from constructive criticism even a "self-proclaimed expert" in the field of forecasting.
