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Descriptive Statistics

Mean, Median and Mode

Mean, Median and Mode are all measures of central tendency.

• Mean, a.k.a. average, is sum of values divided by count of values.
• Median – if we order from smallest to largest, this will be the middle value. For an even number of values, we have two middle values and we split the difference.
• Mode – the most popular value

Question: What are the mean, median and mode of the data below?

Answer: What are the mean, median and mode of the data below?

Standard Deviation

The standard deviation (SD) is a measure of how spread out the numbers are.

In a normal (bell shaped) curve

• 68% within 1 SD of the mean
• 95% within 2 SD of the mean

The Standard Deviation formula

A cautionary tale – Anscombe’s Quartet

Source: Wikipedia