We expect that most LTI students will not need this introduction, at least not the 36-201 component. For an LTI student with a relatively weak background in statistics , 36-217 Probability Theory and Random Processes may be the most appropriate course. It covers the basics of probability theory, random variables, pdfs, limit theorems, etc., and delves a little into random processes and information theory. If you have seen this material before but it was too long ago, this course could be a nice refresher.
Basic calculus is a prerequisite.
36-226 is particularly suitable for LTI students because it covers estimation and hypothesis testing. Both courses require basic calculus. It emphasizes estimation techniques and statistical inference, and uses case studies. It too requires basic calculus. It also requires some coursework in statistics, but your background in LT research may substitute, so check with the instructor.