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Foundations: spreadsheets, data literacy and first SQL · Novice · Lesson 10 of 99 · 13 min video, then about 4 hours of practice
Describing data honestly: averages, spread and distributions
After this you can choose between mean and median, describe spread with standard deviation and percentiles, and read a histogram for skew and outliers.
Why it matters
Most business metrics are skewed: a few customers spend enormously, most spend little. Reporting the mean of a skewed distribution is the single most common way analysts mislead without meaning to. Focus on when the median is the honest summary, what standard deviation does and does not tell you, and why you should always look at the distribution before you summarise it.
How to use this resource
A clear, example-led walk through mean, median, mode, variance and standard deviation.