```Date: Wed, 3 Sep 2003 00:14:51 GMT Reply-To: Greg D Sender: "SAS(r) Discussion" From: Greg D Organization: EarthLink Inc. -- http://www.EarthLink.net Subject: Re: a simple linear extrapolation Hey, Be careful about calling somebody an economist. Now, I am personally a 2-handed economist: on one hand the answer is this, and on other hand the answer could be that. Greg "Ian Whitlock" wrote in message news:9B501B3774931C469BCCCC021BE537223D4983@remailnt2-re01.westat.com... > Jianying, > > A mathematician would say: > > For any two points (x1,y1) and (x2,y2) with x1 ^= x2, then > for any third value x, (x,y) is point on the line passing > through the given points if and only if > > y1-y2 y - y2 > ----- = ------ > x1-x2 x - x2 > > A statistician would say that your sample isn't large enough. > > A physicist would say if x1=x2 then rotate the axes and go to the > mathematician and rotate his answer. > > An engineer would say for year 4 the value is .467803 > > A Republican politician would say this shows we need more money for > military budget and a bigger tax cut. > > A Democratic politician would say George W made the data. > > So you see, we will have to know your occupation before a definitive > answer can be made. Are you an economist by any chance? > > :):):):):) > IanWhitlock@westat.com > -----Original Message----- > From: Zhang, Jianying [mailto:Jianying.Zhang@UMASSMED.EDU] > Sent: Tuesday, August 19, 2003 10:38 AM > To: SAS-L@LISTSERV.UGA.EDU > Subject: a simple linear extrapolation > > > Hi, Dear SAS_L: > > I have completely forgotten how to do a simple linear extrapolation. > > I have three data points and would like to predict the fourth. > > Year 1 .37 > Year 2 .45 > Year 3 .46 > > Do I average the change difference between Year1-Year2 and Year2-Year3??? > And then add the avg change onto the Year 3 value??? > > Thanks in advance > > > Jianying Zhang ```

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