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Vuong's test of zero-inflated against plain Poisson at the boundary

Source: R/ledger_scan.R
morie_zip_vuong_boundary.Rd

At \(\pi = 0\) the zero-inflated Poisson pmf is the Poisson pmf at every count (Research.P7.Cox.zip_zero_eq_poisson), so every pointwise log-likelihood ratio is zero (llr_zero), their sample standard deviation is zero and the Vuong statistic is 0/0, not standard normal.

Usage

morie_zip_vuong_boundary(counts, lam = mean(counts))

Arguments

counts

Observed counts.

lam

Poisson rate; default the sample mean.

Value

A list: llr (all zero), sd (zero) and statistic (NA).

References

Friendly M, Meyer D (2016). Discrete Data Analysis with R, section 11.2. CRC.

Examples

morie_zip_vuong_boundary(c(0, 0, 1, 2, 0, 3))
#> $llr
#> [1] 0 0 0 0 0 0
#> 
#> $sd
#> [1] 0
#> 
#> $statistic
#> [1] NA
#> 
#> attr(,"theorem")
#> [1] "Research.P7.Cox.llr_zero"