Group A \(\displaystyle{x}_{{1}}={2.1}\)

\(\displaystyle{s}_{{1}}={0.7}\)

\(\displaystyle{n}_{{1}}={45}\) Group B \(\displaystyle{x}_{{2}}={1.7}\)

\(\displaystyle{s}_{{2}}={0.4}\)

\(\displaystyle{n}_{{2}}={45}\) \(\displaystyle{S}.{E}.=\sqrt{{{\mathfrak{{a}}}{a}{c}{\left\lbrace{\left({0.7}\right)}^{{2}}\right\rbrace}{\left\lbrace{45}\right\rbrace}+{\frac{{{\left({0.4}\right)}^{{2}}}}{{{45}}}}}}={0.120}\)

\(\displaystyle{d}={x}_{{1}}-{x}_{{2}}={2.1}-{1.7}={0.4}\)

\(\displaystyle{t}_{{c}}{n}_{{c}}{\left({a}{t}{0.10}{l}{o}{s}{\quad\text{and}\quad}{90}-{2}{d}{f}\right)}={1.65}\)

\(\displaystyle\therefore{C}.{I}.={d}\pm{t}_{{c}}{n}_{{c}}{S}.{E}.\)

\(\displaystyle={0.4}\pm{1.65}{\left({0.120}\right)}\)

\(\displaystyle={0.4}\pm{0.198}\)

\(\displaystyle\therefore{C}.{I}.={\left({0.202},{0.598}\right)}\)