o_beta: beta*

In robomit: Robustness Checks for Omitted Variable Bias

Description

Estimates beta*, i.e., the bias-adjusted treatment effect (or correlation) (following Oster 2019).

Usage

o_beta(y, x, con, m = "none", w = NULL, id = "none", time = "none", delta = 1,
R2max, type, data)

Arguments

y	Name of the dependent variable (as string).
x	Name of the independent treatment variable (i.e., variable of interest; as string).
con	Name of related control variables. Provided as string in the format: "w + z +...".
m	Name of unrelated control variables (m; see Oster 2019; as string; default is m = "none").
w	weights (only for weighted estimations). Warning: For weighted panel models R can report different R-square than Stata, leading deviation between R and Stata results.
id	Name of the individual id variable (e.g. firm or farm; as string). Only applicable for fixed effect panel models.
time	Name of the time id variable (e.g. year or month; as string). Only applicable for fixed effect panel models.
delta	delta for which beta* should be estimated (default is delta = 1).
R2max	Maximum R-square for which beta* should be estimated.
type	Model type (either lm or plm; as string).
data	Dataset.

Details

Estimates beta*, i.e., the bias-adjusted treatment effect (or correlation).

Value

Returns tibble object, which includes beta* and various other information.

References

Oster, E. (2019) Unobservable Selection and Coefficient Stability: Theory and Evidence. Journal of Business & Economic Statistics, 37, 187-204.

Examples

# load data, e.g. the in-build mtcars dataset
data("mtcars")
data_oster <- mtcars

# preview of data
head(data_oster)

# load robomit
require(robomit)

# estimate beta*
o_beta(y = "mpg",           # dependent variable
       x = "wt",            # independent treatment variable
       con = "hp + qsec",   # related control variables
       delta = 1,           # delta
       R2max = 0.9,         # maximum R-square
       type = "lm",         # model type
       data = data_oster)   # dataset

Example output

                   mpg cyl disp  hp drat    wt  qsec vs am gear carb
Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1
# A tibble: 10 x 2
   Name                           Value
   <chr>                          <dbl>
 1 Beta*                         -2.00 
 2 (Beta*-Beta controlled)^2      5.56 
 3 Alternative Solution 1        -7.01 
 4 (Beta[AS1]-Beta controlled)^2  7.05 
 5 Uncontrolled Coefficient      -5.34 
 6 Controlled Coefficient        -4.36 
 7 Uncontrolled R-square          0.753
 8 Controlled R-square            0.835
 9 Max R-square                   0.9  
10 Detla (defined)                1    

robomit documentation built on June 22, 2021, 9:09 a.m.