3. (4pt, R required) Find the necessary sample size to achieve at least 80% power when pa = 200, the true mean (u) varies from 210, to 220, 230, and the standard deviation varies from 10, 15, to 20 (all possible combinations). Assuming (1:0.05, two tailed. Use your calculator or R for the calculation. Draw a sample size plot similar to the one presented in the lecture. Specifically, the xaxis is the standard deviation, yaxis is the required sample size, and lines with different colors correspond to different mean difference (u H0)- Power Sample size calculation (alpha: 0.05, power: 0.8) N Per Group 400 300 200 100 I Mean Diff i 10 i 20 so i 40 \\\\\\':411