ECON440
Fall 2020
Binary Dependent Variable
Believe it or not, workers used to be able to smoke inside office buildings. Smoking bans were introduced in several
areas during the 1990s. In addition to eliminating the
...
ECON440
Fall 2020
Binary Dependent Variable
Believe it or not, workers used to be able to smoke inside office buildings. Smoking bans were introduced in several
areas during the 1990s. In addition to eliminating the externality of secondhand smoke, supporters of these bans argued that they
would encourage smokers to quit by reducing their opportunities to smoke. In this assignment you will estimate the effect of
workplace smoking bans on smoking, using data on a sample of 10,000 U.S. indoor workers from 1991 to 1993, available in the
file Smoking. The data set contains information on whether individuals were or were not subject to a workplace smoking ban,
whether the individuals smoked, and other individual characteristics.
a. Estimate the probability of smoking for
i. All workers (Table 5)
Mean probability of smoking for all workers is 0.242
ii. Workers affected by workplace smoking bans (Table 5)
Mean probability of smoking if smkban = 1 is 0.212
iii. Workers not affected by workplace smoking bans (Table 5)
Mean probability of smoking if smkban = 0 is 0.2896
b. What is the difference in the probability of smoking between workers affected by a workplace-smoking ban and workers not
affected by a workplace-smoking ban? Use a linear probability model to determine whether this difference is statistically
significant.
Difference of mean probability: 0.212 – 0.2896 = -0.0776
Using a linear regression model (Table 6), we find that the coefficient is -0.077558, and the difference is statistically
significant (F = 78.6, p = 0.00)
c. Estimate a linear probability model with smoker as the dependent variable and the following regressors: smkban, female, age,
age2, hsdrop, hsgrad, colsome, colgrad, black, hispanic. Compare the estimated effect of a smoking ban from this regression with
your answer from (b). Suggest a reason, based on the substance of this regression, explaining the change in the estimated effect of
a smoking ban between (b) and (c).
The coefficient of smkban is -0.0472 (Table 7), which is smaller than the one in (b). The result in (b) is likely to suffer
from omitted variable bias, which the multiple-regression model takes into account. For example, college graduates are less likely
to smoke than high school dropouts.
d. Test the hypothesis that the coefficient on smkban is zero in the population version of the regression in (c) against the alternative
that it is nonzero, at the 5% significance level.
We can perform a t-test on this hypothesis: H0: βsmkban = 0, H1: βsmkban != 0
t = (-0.0472 – 0)/0.00897 = -5.262
Since |t| > 1.96, we can reject the null hypothesis at the 5% significance level.
e. Repeat (c) using a probit model. (Table 8)
t = (-.1586 – 0)/0.029 = -5.45
Since |t| > 1.96, we can reject the null hypothesis at the 5% significance level.
f. Repeat (c) using a logit model. (Table 9)
t = (-0.262 – 0)/0.0495 = -5.293
Since |t| > 1.96, we can reject the null hypothesis at the 5% significance level.
g.
i. Mr. A is white, non-Hispanic, 20 years old, and a high school dropout. Using the probit regression and assuming that Mr. A
is not subject to a workplace-smoking ban, calculate the probability that Mr. A smokes. Carry out the calculation again,
assuming that he is subject to a workplace-smoking ban. What is the effect of the smoking ban on the probability of
smoking?
1. P(A|smok=1,smkban=0) = Φ (-1.735 + 20*0.0345 – 20^2*0.00047 + 1*1.142) = Φ(0.09) = 0.464
2. P(A|smok=1,smkban=1) = Φ (-1.735 – 1*0.1586 + 20^2*0.0345 – 20*0.00047 + 1*1.142) = Φ (-0.24) = 0. 402
The effect of the smoking ban is 0.464 – 0.402 = 0.062 = 6.2%
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