Lecture notes.md

Personal lecture/textbook notes for an Intro Statistics course, jotted for exam preparation. The notes span four lectures and form the raw material for this study wiki. [Lecture notes.md]

• Mean is sensitive to outliers; median is preferred for skewed data (e.g. income). [Lecture notes.md]
• Variance uses squared deviations (plain deviations sum to zero); standard deviation brings units back to the original scale. [Lecture notes.md]
• The 68-95-99.7 rule describes what proportion of data falls within 1, 2, and 3 standard deviations of the mean in a normal distribution. [Lecture notes.md]
• In a perfectly normal distribution, mean = median = mode. [Lecture notes.md]
• Correlation coefficient r ranges from −1 to 1; r = 0 signals no *linear* relationship (nonlinear patterns may still exist). Correlation does not imply causation — watch for confounders and reverse causation. [Lecture notes.md]

• Central Tendency (Mean / Median / Mode)
• Spread (Variance & Standard Deviation)
• Normal Distribution
• Correlation vs Causation

Notes are structured as Cornell notes (key concepts + cue questions + one-line summary). Head to Review & Spaced Repetition to practice all cue questions and follow the spaced-review calendar.