Inferential Statistics

I sort of caught up with a mixture of some very good MOOCs:

• improving your statistical inferences by Eindhoven University of Technology is fantastic
• inferential statistics by University of Amsterdam is great
• statistical inference by John Hopkins is also great

And working through my own statistical problems by asking people on stats.stackexchange and other forums.

Yes, there are many free courses that you can use to learn the prerequisite mathematics. KhanAcademy would be my first recommendation, but you can also try some of these:

Inferential Statistics https://www.coursera.org/learn/inferential-statistics

Bayesian Statistics: From Concept to Data Analysis https://www.coursera.org/learn/bayesian-statistics

Inferential Statistics Intro https://www.coursera.org/learn/inferential-statistics-intro

Bayesian Statistics https://www.coursera.org/learn/bayesian

Basic Statistics https://www.coursera.org/learn/basic-statistics

Introduction to Probability https://www.edx.org/course/introduction-probability-science-mitx-6-041x-2

Introduction to Linear Models and Matrix Algebra https://www.edx.org/course/introduction-linear-models-matrix-harvardx-ph525-2x-2

Intro to Descriptive Statistics https://www.udacity.com/course/intro-to-descriptive-statistics--ud827

Intro to Inferential Statistics https://www.udacity.com/course/intro-to-inferential-statistics--ud201

Mathematics for Computer Science https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-042j-mathematics-for-computer-science-fall-2010/index.htm

An Intuitive Introduction to Probability https://www.coursera.org/learn/introductiontoprobability

Statistical Inference https://www.coursera.org/learn/statistical-inference

College Algebra and Problem Solving https://www.edx.org/course/college-algebra-problem-solving-asux-mat117x

Precalculus https://www.edx.org/course/precalculus-asux-mat170x