Stage 2 · Lesson 8 of 9
Descriptive statistics
Before modelling anything, summarise it. The is the average, the median is the middle value, and the standard deviation is the typical distance from the mean. and the interquartile range (the spread of the middle half of the data) describe spread without being thrown by extremes.
Correlation measures how closely two variables move together in a straight line, from -1 to 1. These numbers are the first thing you check when exploring data, and the words you use to explain results.
Common trapThe traps are well known but keep repeating. The mean is dragged by : one billionaire makes average income meaningless, so the median is better. A correlation near zero does not mean no relationship, only no straight-line one. And correlation never proves causation on its own.
A question to check yourself, an AI practice session and 1 cheat sheet entry come with the full roadmap. Unlock
Resources for this stage
Start with· follow one of these
- CoursePaidMathematics for Machine Learning and Data Science Specialization
DeepLearning.AI · Beginner · Coursera subscription; financial aid available
Paid, with financial aid: linear algebra, calculus and statistics taught visually with Python labs
- CourseFreeKhan Academy Statistics and Probability
Khan Academy · Beginner
Free, complete statistics and probability with practice questions on every topic
Keep handy
Also worth your time
- Mathematics for Machine LearningGo deeper
Free book that ties the maths directly to regression, PCA and classifiers