n <- 12
x <- 100  # Total of 12 observations
# Exact CI: poisson.test(x, n)$conf.int
# Derive asymptotic CI for poisson rate

# Coef of var
xx <- seq(-3, 3, length=101)
plot(xx, xx^2, col='slateblue', type='l', bty='n', lwd=3, xlab=expression(mu), ylab=expression(sigma^2), las=1)