Update status: The latest version of Lertap 5 is 5.10.99. It is available at Lertap.com and may be reached by following "Useful link" (1). This version will run with Excel 2016 on either a Windows or a Macintosh computer (it will also run with Excel 2010 on Windows computers, but not with Excel 2007).
Here's a brief description of each of the "Useful links" found further down the page:
(1) corresponds to the ReadMeMacWin.pdf file, used to install Version 5.10.99. This version is free. It will work with Excel 2010, Excel 2013, and Excel 2016 under Windows, and with Excel 2016 on a Macintosh. It installs as a fully functional version, limited to processing results from no more than 100 students or survey responders, a limit which may be removed by obtaining an activation key (free for students).
(2) links to webpages describing how to upgrade Lertap so that it is not restricted to 100 data records.
(3) links to the "updates summary" for all versions of Lertap.
(4) links out to a website with sample datasets.
(5) will take you to a website with some very practical pointers on using Excel and Lertap (includes numerous examples of Lertap and Excel in action).
(6) and (7) are instructive YouTube videos about Lertap, produced by Tony Davidson.
(8) links to class references used by Larry Nelson in the year 2018
(9) and (10) go to examples of IRT analyses using R packages
(11) a polytomous IRT example for use with RStudio; uses data from the BFI-25 study
(98) takes you out to the Lertap 5 e-store