Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
st: problem with squared term
From
Prabhat <[email protected]>
To
[email protected]
Subject
st: problem with squared term
Date
Sun, 21 Mar 2010 02:42:19 +0900
Dear all,
I have come across a strange problem. I am trying to estimate the
coefficients for temperature and rainfall using WLS, where my
dependent variable is rice yield.
Now, when I am including the square term for the average temperature,
I am getting a very high and impossible estimate for the temperature
variable. It should be somewhere between 100-300, but after including
square term I am getting -3500.
I have just included OLS results here.
Any comment will be appreciated.
Regards,
Prabhat Barnwal
International University of Japan
> . regress kyrice kavgtemp kavgtempsq ktotppt ktotpptsq ksdtemp
Source | SS df MS Number of obs = 735
-------------+------------------------------ F( 5, 729) = 13.16
Model | 21551254.8 5 4310250.95 Prob > F = 0.0000
Residual | 238840813 729 327628.001 R-squared = 0.0828
-------------+------------------------------ Adj R-squared = 0.0765
Total | 260392067 734 354757.585 Root MSE = 572.39
------------------------------------------------------------------------------
kyrice | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
kavgtemp | -3591.648 855.2294 -4.20 0.000 -5270.655 -1912.642
kavgtempsq | 67.01803 15.34115 4.37 0.000 36.89993 97.13613
ktotppt | 1.053627 .5836936 1.81 0.071 -.0922936 2.199548
ktotpptsq | -.0005872 .0003753 -1.56 0.118 -.001324 .0001496
ksdtemp | -196.4774 56.57082 -3.47 0.001 -307.5386 -85.41624
_cons | 49759.5 11888.92 4.19 0.000 26418.9 73100.1
------------------------------------------------------------------------------
-> . regress kyrice kavgtemp ktotppt ktotpptsq ksdtemp
Source | SS df MS Number of obs = 735
-------------+------------------------------ F( 4, 730) = 11.39
Model | 15298828.3 4 3824707.07 Prob > F = 0.0000
Residual | 245093239 730 335744.163 R-squared = 0.0588
-------------+------------------------------ Adj R-squared = 0.0536
Total | 260392067 734 354757.585 Root MSE = 579.43
------------------------------------------------------------------------------
kyrice | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
kavgtemp | 143.2145 22.12018 6.47 0.000 99.78776 186.6413
ktotppt | .9560253 .5904461 1.62 0.106 -.2031498 2.1152
ktotpptsq | -.00057 .0003799 -1.50 0.134 -.0013158 .0001758
ksdtemp | -213.2879 57.13459 -3.73 0.000 -325.4556 -101.1202
_cons | -2107.959 622.1736 -3.39 0.001 -3329.422 -886.4957
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/