The Degrees of Freedom Used When Testing Two Independent Samples $\mathrm { n } _ { 1 } - 1$

The degrees of freedom used when testing two independent samples where the population standard deviation is unknown is

A) the smaller of $\mathrm { n } _ { 1 } - 1$ or $\mathrm { n } _ { 2 } - 1$ .
B) the larger of $\mathrm { n } _ { 1 } - 1$ or $\mathrm { n } _ { 2 } - 1$ .
C) $n _ { 1 } + n _ { 2 } - 2$
D) $n _ { 1 } + n _ { 2 } - 1$ . 2 Construct and interpret confidence intervals regarding the difference of two independent means.