Please solve question no. 57

C o m b i n e d M e a n (\bar{X_{12}}) = \frac{N_{1} \bar{X_{1}} + N_{2} \bar{X_{2}}}{N_{1} + N_{2}} = \frac{50 \times 63 + 40 \times 54}{50 + 40} = \frac{3150 + 2160}{90} = 59 C o m b i n e d s \tan d a r d d e v i a t i o n = \sqrt{\frac{N_{1} {σ_{1}}^{2} + N_{2} {σ_{2}}^{2} + N_{1} (\bar{X_{1 -}} \bar{X_{12}})^{2} + N_{2} (\bar{X_{2 -}} \bar{X_{12}})^{2}}{N_{1} + N_{2}}} = \sqrt{\frac{(50 \times 9^{2}) + (40 \times 6^{2}) + (50 \times 4^{2}) + (40 \times 5^{2})}{40 + 50}} = 9

View Full Answer