Re: basic regression question

Hello Sab,

In your model the two time series play very important role. First find
out is there any difference between this time series based on
independent variable. This you can do by T-Test or you can do under
Custom tables Test Statistic option(This is purely drag and drop only).

If time series 1 is significantly differ from time series 2, then your
conclusion is correct for time series 1 based model.

For the time series 2 model, it's also may be the reason

1) Less sample size (for regression 30 cases adequate)
In this case just increase the sample size and check your R
square value.

2) Whether if the time period really affects your model...that time you
need to consider/add some other (related) parameters.

--check the correlation value and scatter plot for
dependent and independent based time series. This will help you to
identify the slope graphically.


3) Separate the data file half and do the regression for each set and
check the R square value. If R square value is satisfied, the reason 2
is correct. i.e., your model purely affected by time and some other
factors too.


Here is two links, this also give some more information for you.

http://www.stat.umn.edu/users/stat-lisp-news/msg00005.html
http://www.ats.ucla.edu/stat/SPSS/faq/dummy.htm

If it is possible, can you send the data file? I will take a look.


Thanks,

Lawrence.

.

Relevant Pages

  • Re: Is time series analysis available in Excel 2003?
    ... my book is not available as a download. ... Excel already had analysis tools that allowed you to designate the input ... independent variable and whether you want to force the regression thru the ... Regression and worksheet formulas can be used for time series analysis. ...
    (microsoft.public.excel.misc)
  • Re: cointegrated time series regression analysis
    ... Modeling time series using Regression methods ... There are many ways of ANALYZING and MODELING time series. ... Multiple Regression methods using the LAGS and DIFFERENCES ...
    (sci.stat.math)
  • Re: Multivariate Analysis
    ... >X affects the price of a product. ... >Adaptive Regression Splines) that seemed as though it would help me. ... You have a time series problem and should read about "time series ... to out-of-sample prediction. ...
    (sci.math.num-analysis)
  • Re: Multivariate Analysis
    ... >X affects the price of a product. ... >Adaptive Regression Splines) that seemed as though it would help me. ... You have a time series problem and should read about "time series ... to out-of-sample prediction. ...
    (sci.stat.math)
  • Multiple simple regressions procedure?
    ... I have about 100 stock time series as colums in a sheet to be used as ... dependent variables in the regression. ... span for the regression that is used to derive the market model. ...
    (microsoft.public.excel.misc)