1.7 | Summary Stats (STDev, Variance, Mean)

What is standard deviation (stdev) a measure of?

The average distance of data points from the mean.

What is the symbol for sample standard deviation?

s

What is the symbol for population standard deviation?

σ

What is the symbol for population mean?

μ

What is the symbol for sample mean?

x̄

What is the symbol for population variance?

σ²

What is the symbol for sample variance?

s²

What is the mathematical definition of an outlier, in terms of IQR?

A data point that lies >=1.5 times the interquartile range (IQR) below Q1 or above Q3.

What is the mathematical definition of an outlier, in terms of standard deviation?

A data point that lies more than 2 standard deviations away from the mean.

Of the following, which are heavily affected by skew and outliers?

• Mean

• Median

• Standard deviation

• IQR

Mean and standard deviation

Of the following, which are relatively unaffected by skew and outliers?

• Mean

• Median

• Standard deviation

• IQR

Median and IQR