Statistics designed to answer questions such as central tendency, spread/variability, extreme values are called summary statistics.
This recipe includes the following topics:
- Mean
- Variance and Standard deviation
- Effect Size
- Cohen’s d
Mean
- Mean is the most common summary statistic used to describe the central tendency of the distribution.
- Useful when samples are pretty similar. Eg: Size of an apple in a supermarket are mostly similar.
Mean
Variance and Standard deviation
- Variance is a summary statistic often used to quantify spread.
- Standard deviation is the square root of variance, also used as a measure of spread.
- Useful when samples vary widely.
- Eg: Pumpkin can weigh between 1lb to 400lb. Both mean and variance may be needed to describe the distribution.
Variance
Effect size and Cohen’s d
- Effect size is a summary statistic intended to quantify the size of an effect.
- Eg: Size of an effect in two groups where Group A was given Medicine A but Group B was given none.
- Cohen’s d is intended to measure this effect size.
Cohen’s d