* do-file for Supplementary Exercises 2.11, 2.48, 10.38 and 10.39 of IPS7e
version 17 /* works also with versions 13-16 */

import delimited "R:\Chapter 2\ex02_011.csv"
scatter hav ma
pwcorr hav ma, sig
twoway (scatter hav ma) (lfit hav ma)
regress hav ma

* Stata does not give a prediction interval but it can be computed
* from the fitted value, the prediction ("forecast") error and the t-percentile
* To get the values for MA=25, look for an observation with that value!
predict fit, xb
predict pe_fit, stdf
display invttail(36,0.025) /* our t-star value */
generate pi_lower = fit - invttail(36,0.025)*pe_fit
generate pi_upper = fit + invttail(36,0.025)*pe_fit

* analyses without the suspected outlier
pwcorr hav ma if hav<50, sig
regress hav ma if hav<50