| `install.packages("pwr")` | |
| `library(pwr)` | |
| #### INPUT THE SAMPLE SIZES, MEAN CALVING SUCCESS AND STANDARD ERRORS FROM MANN, ET AL. 2008. | |
| ``` | |
| # Non-spongers: | |
| n_nonspongers=116 | |
| mean_CS_nonspongers=0.132 | |
| SE_CS_nonspongers=0.008 | |
| # Spongers: | |
| n_spongers=16 | |
| mean_CS_spongers=0.156 | |
| SE_CS_spongers=0.018 | |
| #### CALCULATE DIFFERENCE IN MEASURED CALVING SUCCESS BETWEEN SPONGERS AND NONSPONGERS | |
| percent_increase=(mean_CS_spongers - mean_CS_nonspongers)/mean_CS_nonspongers | |
| print(paste("Percent Increase in Sponger Calving Success: ", 100*round(percent_increase, digits=2), "%")) | |
| ``` | |
| #### CONVERT STANDARD ERRORS TO STANDARD DEVIATIONS | |
| ``` | |
| SD_CS_nonspongers=SE_CS_nonspongers*sqrt(n_nonspongers) | |
| SD_CS_spongers=SE_CS_spongers*sqrt(n_spongers) | |
| ``` | |
| #### CALCULATE TERMS FOR POWER ANALYSIS | |
| ``` | |
| SS_within=(n_nonspongers-1)*SD_CS_nonspongers^2 + (n_spongers-1)*SD_CS_spongers^2 | |
| df_within=n_nonspongers + n_spongers - 2 | |
| SD_within=sqrt(SS_within/df_within) | |
| ``` | |
| #### PERFORM POWER ANALYSIS FOR A TWO-SIDED TEST | |
| ``` | |
| ## RUN POWER ANALYSIS | |
| power_test_results=pwr.t2n.test(n1=n_nonspongers, n2=n_spongers, d=NULL, sig.level = 0.05, power = 0.8, | |
| ``` |