A personal trainer is studying whether a new stretching routine improves flexibility. She records the forward reach (in cm) of 6 clients before and after a 4-week program. Calculate the difference (after - before) for each client, the mean difference, and standard deviation.

Difference for each client: $A=4,B=4,C=3,D=-1,E=0,F=2$; The Mean Difference = $2$; and Standard Deviation = $1.91$

Difference for each client: $A=4,B=4,C=3,D=-1,E=0,F=2$; The Mean Difference = $2.5$; and Standard Deviation = $1.91$

Difference for each client: $A=4,B=4,C=3,D=-1,E=0,F=2$; The Mean Difference = $2.5$; and Standard Deviation = $2.10$

Difference for each client: $A=4,B=4,C=3,D=-1,E=0,F=2$; The Mean Difference = $2$; and Standard Deviation = $2.10$