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

# Coefficient of variation: Curved exponential family
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
)