What is the difference between mean, median, and mode? ▾
Mean is the arithmetic average (sum ÷ count). Median is the middle value when sorted. Mode is the most frequent value. They all describe the "centre" of a dataset but react differently to outliers.
When should I use a weighted average? ▾
Use weighted average when different values have different importance. Examples: GPA (courses with more credits count more), investment portfolio returns (larger positions carry more weight), grade calculations with different assignment weights.
Why can the mean be misleading? ▾
Outliers skew the mean heavily. For example, if 9 people earn $30,000 and one earns $1,000,000, the mean income is $127,000 — not representative of anyone's actual income. The median ($30,000) would be more accurate here.