What symbol is used for the standard deviation when it is a sample statistic? What symbol is used for the standard deviation when it is a population parameter?

Sample statistic: $\sigma $. Population parameter: s.

For both, s is used.

For both, $\sigma $ is used.

Sample statistic: s. Population parameter: $\sigma $.

Sample statistic: $\sigma $. Population parameter: s.

For both, s is used.

For both, $\sigma $ is used.

Sample statistic: s. Population parameter: $\sigma $.