Calculate upper control limit (UCL)

Basic formula for UCL: estimated mean + 3 * estimated standard deviation

ucl(theta_hat, n_new, factor_sd = 3)

Arguments

theta_hat

Estimate (unless known) of rate parameter theta

n_new

New value for exposure (reference counts), must at least be 1

factor_sd

Factor multiplying standard deviation (default: 3)

Value

UCLs

Details

In this case, assuming a Poisson distribution, both the estimated mean and the estimated variance are lambda_hat = theta_hat * n_new.

Rounds the result to the nearest integer.

Adds 0.5, so that count values are either above or below the UCL (as in Wheeler & Chambers [1992]).