# newLISP® v.10.5.4 Stable Release 2013-10-1

This stable release fixes bugs and adds two new call patterns to the `t-test` function.

### Additions

- A call pattern for the one sample `t-test` has been added to compare the sample mean to a number given as a parameter.
- The Welch variant of the `t-test` has been added to be used when variances in the two data samples differ significantly. The new call pattern allows an automatic switch between the normal and Welch method of Student's t when specifying a critical probability value for the null hypothesis of variances being equal.

### Bug fixes

- A fix for last list-element optimization in `pop` and `pop-assoc` when popping and then inserting a last element in nested lists.
- Accessing a deleted context will never hang but give an error message.

### Other changes

- The build process for OSX newLISP binary installers has been simplified.

### Compatibility with previous versions

This version is compatible with the previous versions in the 10.5.x series.

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