This is personal study note Copyright and original reference: https://www.youtube.com/watch?v=WDjc2Ie-oY8&list=PLsri7w6p16vulKaxOlNQFSWuyDuE9oEVP&index=5 ================================================================================ Interval of population's variance variance distribution of one sample: $$$\chi^2$$$ distribution variance distribution of two sample: F distribution ================================================================================ chi-square sample=extract_sample(n,population) $$$s^2$$$=get_sample_variance(sample) dof,dist=calculate_variance_distribution($$$s^2$$$) dof=$$$n-1$$$ dist: $$$\chi^2$$$ distribution ================================================================================ chi-square distribution in graph min and max in "interval estimation" $$$\chi^2_{1- \frac{\alpha}{2}} \le \frac{(n-1)s^2}{\sigma^2} \le \chi^2_{\frac{\alpha}{2}}$$$ ================================================================================ Example