STA215H5 Chapter Notes - Chapter 5: Standard Deviation, Frequency Distribution, Normal Distribution
Document Summary
Chapter 5 the standard deviation as a ruler and the normal model. Expressing a distance from the mean in standard deviations standardizes the performances. To standardize a value, we subtract the mean and then divide this difference by the standard deviation: By using the standard deviation as a ruler to measure statistical distance from the mean, we can compare values from the same data set, or even two values measured on different variables or with different scales. There are 2 steps to finding a z-score: first the data are shifted by subtracting the mean, then they are rescaled by dividing by the standard deviation. Adding (or subtracting) a constant to every data value adds (or subtracts) the same constant to measures of position (centre, percentiles, min, max), but leaves measures of spread unchanged (range, iqr, standard deviation) Multiplying or dividing each value by a constant rescaling the data changes the measurement units.
