Mean, variance and distributions

After this lesson you can: Describe a dataset's centre and spread, and read a histogram.

Watch

• Calculating the Mean, Variance and Standard Deviation, Clearly Explained!!! - StatQuest with Josh Starmer, 14 min. Directly targets mean, variance, and standard deviation with beginner-friendly StatQuest framing and ideal concept length.
• The Main Ideas behind Probability Distributions - StatQuest with Josh Starmer, 5 min. Adds the distribution mental model needed to move beyond single-number summaries of datasets.
• The Normal Distribution, Clearly Explained!!! - StatQuest with Josh Starmer, 5 min. Introduces a common distribution shape engineers will repeatedly see when reading histograms and model outputs.

Notes

The mean is a way to describe the centre of a dataset: add the values and divide by how many values there are. It answers “where is this data roughly centred?” but not “what does the data look like?” Two datasets can have the same mean while behaving very differently: one might have values tightly packed near the mean, while another might have values spread widely or split into separate groups.

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