Additionally ... also

[disclosure: I'm not a native speaker of English]

I work as a university professor. When writing up lecture notes as well as research papers, I have a tendency to write things like the following.

A Monte Carlo simulation shows that Factor A is a significant one. Additionally, it also shows that the outliers can be grouped together as a special case.

The question is whether the Additionally...also sequence is a stylistically acceptable one, given that both additionally and also convey additivity. I keep on using it because using just one of the two sounds weird, in a way that I really can't put my finger on (but then, this might be because I don't speak English natively).

If Additionally...also is deprecated, I would welcome suggestions of alternative ways of expressing the same meaning.

I agree that additionally...also appears redundant, although it can be used appropriately when you're saying, essentially, that in addition to the aforementioned, they show xyz as well. However, a single also or in addition is not strange to my native AmE ears. In most cases, therefore, I would avoid that construction.

This Ngram shows how much more frequent In addition is than Additionally to start a sentence.

So, you can write

The simulation also shows that the outliers can be grouped together as a special case. or In addition, it shows..."

I agree with medica's recommendation that you either (1) use "In addition" rather than than "Additionally" at the beginning of the sentence and omit "also," or (2) omit "In addition" (and "Additionally") from the beginning of the sentence and retain "also."

Another option is to begin the second sentence with "Also," although some style mavens—and some publishing houses that follow their dictates—disapprove of this tactic (for reasons I've never fully understood):

A Monte Carlo simulation shows that Factor A is significant. Also, it shows that the outliers can be grouped together as a special case.

If you want to vary your wording beyond the trio of "in addition," "additionally," and "also" in such situations, you have several other alternatives. One approach is to begin the sentence with "Moreover," "Further," or "Furthermore," omitting the "also" in each case:

A Monte Carlo simulation shows that Factor A is significant. Moreover/Further/Furthermore, it shows that the outliers can be grouped together as a special case.

Yet another approach is to omit the "also" and add "too" or "as well" in an appropriate Ilocation:

A Monte Carlo simulation shows that Factor A is significant. It shows, too/as well, that the outliers can be grouped together as a special case.