* Prediction
* Reference: Chapters 3 and 5 of
*    R. Carter Hill, William E. Griffiths and George G. Judge, 
*    Undergraduate Econometrics, Second Edition, Wiley. 
* 
* Use the DIM command to allocate space for the variables
DIM FOOD 41 INCOME 41 YHAT 41 SE 41
* Set a value for income for the prediction exercise
SAMPLE 41 41
GENR INCOME=750 
* Load the data set
SAMPLE 1 40
READ (TAB3-1.shd) FOOD INCOME / SKIPLINES=1
* Least squares estimation
OLS FOOD INCOME
* Prediction (Equation 3.3.15, p.57 and Section 5.3.1, p.113)
FC / LIST BEG=41 END=41 PREDICT=YHAT FCSE=SE
* Note: the calculated residual and prediction diagnostics from
* FC are not meaningful since there is no observed value for FOOD.

* Calculate a 95% prediction interval (Section 5.3.1, p.113).
* Obtain the critical value.
GEN1 DF=$N-$K
SAMPLE 1 1
GEN1 ALPHA=0.05/2
DISTRIB ALPHA / TYPE=T DF=DF INVERSE CRITICAL=TC
PRINT TC
SAMPLE 41 41
GENR YUP=YHAT+TC*SE
GENR YLOW=YHAT-TC*SE
* Print the prediction interval
PRINT YLOW YUP
STOP