Wooldridge Textbook Example

[Jacky Lin]

Hi I am trying to replicate one example from Wooldridge. Here is the equation.

This is the link for the data, Sorry about that I don't know how to upload the data set.

http://qcpages.qc.cuny.edu/~rvesseli...ata/JTRAIN.DTA

I try a couple time, but can not replicate this two outcomes. Really appreciate if anyone can help me solve this two problems and show the command. Thank you!

Best,

Jacky

[Chen Samulsion]

I don't konw which textbook of Jeff Wooldridge that you used, and so I don't know its page and context. I try to replicate the results by using following codes:

by fcode: gen dscrap = scrap - scrap[_n-1]
by fcode: gen dlscrap = lscrap - lscrap[_n-1]
reg dscrap grant if year==1988
reg dlscrap grant if year==1988

. by fcode: gen dscrap = scrap - scrap[_n-1]
(363 missing values generated)

. by fcode: gen dlscrap = lscrap - lscrap[_n-1]
(363 missing values generated)

. reg dscrap grant if year==1988

      Source |       SS           df       MS      Number of obs   =        54
-------------+----------------------------------   F(1, 52)        =      1.17
       Model |  6.73345587         1  6.73345587   Prob > F        =    0.2837
    Residual |  298.400031        52  5.73846213   R-squared       =    0.0221
-------------+----------------------------------   Adj R-squared   =    0.0033
       Total |  305.133487        53   5.7572356   Root MSE        =    2.3955

------------------------------------------------------------------------------
      dscrap |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
       grant |  -.7394436   .6826276    -1.08   0.284    -2.109236    .6303488
       _cons |  -.5637143   .4049149    -1.39   0.170    -1.376235    .2488069
------------------------------------------------------------------------------

. reg dlscrap grant if year==1988

      Source |       SS           df       MS      Number of obs   =        54
-------------+----------------------------------   F(1, 52)        =      3.74
       Model |  1.23795567         1  1.23795567   Prob > F        =    0.0585
    Residual |  17.1971851        52  .330715099   R-squared       =    0.0672
-------------+----------------------------------   Adj R-squared   =    0.0492
       Total |  18.4351408        53  .347832845   Root MSE        =    .57508

------------------------------------------------------------------------------
     dlscrap |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
       grant |  -.3170579   .1638751    -1.93   0.058    -.6458974    .0117816
       _cons |  -.0574357    .097206    -0.59   0.557    -.2524938    .1376224
------------------------------------------------------------------------------

[Jacky Lin]

I don't konw which textbook of Jeff Wooldridge that you used, and so I don't know its page and context. I try to replicate the results by using following codes:

by fcode: gen dscrap = scrap - scrap[_n-1]
by fcode: gen dlscrap = lscrap - lscrap[_n-1]
reg dscrap grant if year==1988
reg dlscrap grant if year==1988

. by fcode: gen dscrap = scrap - scrap[_n-1]
(363 missing values generated)

. by fcode: gen dlscrap = lscrap - lscrap[_n-1]
(363 missing values generated)

. reg dscrap grant if year==1988

Source | SS df MS Number of obs = 54
-------------+---------------------------------- F(1, 52) = 1.17
Model | 6.73345587 1 6.73345587 Prob > F = 0.2837
Residual | 298.400031 52 5.73846213 R-squared = 0.0221
-------------+---------------------------------- Adj R-squared = 0.0033
Total | 305.133487 53 5.7572356 Root MSE = 2.3955

------------------------------------------------------------------------------
dscrap | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
grant | -.7394436 .6826276 -1.08 0.284 -2.109236 .6303488
_cons | -.5637143 .4049149 -1.39 0.170 -1.376235 .2488069
------------------------------------------------------------------------------

. reg dlscrap grant if year==1988

Source | SS df MS Number of obs = 54
-------------+---------------------------------- F(1, 52) = 3.74
Model | 1.23795567 1 1.23795567 Prob > F = 0.0585
Residual | 17.1971851 52 .330715099 R-squared = 0.0672
-------------+---------------------------------- Adj R-squared = 0.0492
Total | 18.4351408 53 .347832845 Root MSE = .57508

------------------------------------------------------------------------------
dlscrap | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
grant | -.3170579 .1638751 -1.93 0.058 -.6458974 .0117816
_cons | -.0574357 .097206 -0.59 0.557 -.2524938 .1376224
------------------------------------------------------------------------------

Hi Samulsion,

Thank you so much! Sorry I forget given the textbook information. It's Professor Jeff's Introductory Econometrics: A Modern Approach 6th Edition. Chapter 13, page 418. Thank you so much for your command again!

Best,

Jacky

[Chen Samulsion]

Hi Lin, thanks for feedback, you can also use time-series operators -- D. here -- to simplify your commands line; and also see help tsvarlist

xtset fcode year
regress D.scrap grant if year==1988
regress D.lscrap grant if year==1988

[Jacky Lin]

Hi Lin, thanks for feedback, you can also use time-series operators -- D. here -- to simplify your commands line; and also see help tsvarlist

xtset fcode year
regress D.scrap grant if year==1988
regress D.lscrap grant if year==1988

Hi Samulsion, Thank you so much!

Best,

Jacky