Riddle: Estimate effect of x on y if you only have two noisy measures of x.

Consider the following data generating process:

set.seed(1)
n = 100000
x = rnorm(n)

eta1 = rnorm(n) # measurement error1
noisy1 = x + eta1

eta2 = rnorm(n) # measurement error2
noisy2 = x + eta2

u = rnorm(n)
beta0=0; beta1 = 1
y = beta0+beta1*x + u
…