# Likelihood tools

**Likelihood** This procedure will enter an Excel array formula to
calculate the negative log likelihood for a set of observed data
assuming observational uncertainty. You must first use the
spreadsheet to develop an explanatory model. The data ranges (model
and observed) must be the same size and shape. Currently only
Normal, Poisson, Multinomial and Binomial likelihoods are allowed.
For Multinomial likelihoods, you must choose a range containing the
observed data and choose a range containing the cell probabilities.
Binomial likelihoods can be specified using Multinomial with two
cells, though it would be more efficient to use Excel’s built-in
formula BINOMDIST.

**Bootstrap iteration**This routine uses**** Solver to compute
confidence limits for a set of parameters by bootstrapping. You
must first enter a PopTools array formula to resample the data.
Then use the Likelihood routine (or some other method) to calculate
the likelihood for the bootstrap sample. The routine works by
replacing the bootstrap sample with fixed values and then calling
Solver to fit the parameters. The bootstrap sample is then
recalculated to generate a new sample. This is repeated many times,
yielding a distribution of parameter estimates, from which
confidence limits can be calculated. The output is a new sheet
containing the parameter estimates for each iteration. Sort the
data and then use the “Summary stats” routine to get the
percentiles.

**Likelihood profile**This routine uses**** Solver to create a
likelihood profile and 95% confidence limits for a single
parameter. Before invoking this routine, you must

- install Solver (use TOOLS/ADD-INS),
- use the spreadsheet to calculate the likelihood based on a single parameter set,
- have a single cell containing the sum of the negative log likelihood for the model, and
- find the point estimates using Solver.

**Summary Stats**. See this page.