# ============================================================
# Sample Size & Power
# Biostatistics in R — Rverse Analytics
# https://rverseanalytics.com/learn-biostatistics/power
# ============================================================

# Sample size & power for a two-group t-test
# n per group for 80% power (delta = 5, sd = 10)
power.t.test(delta = 5, sd = 10, power = 0.80, sig.level = 0.05)
# Power for a fixed n = 30 per group
power.t.test(n = 30, delta = 5, sd = 10, sig.level = 0.05)
# With the pwr package: effect size d = 0.5
library(pwr)
pwr.t.test(d = 0.5, power = 0.80, sig.level = 0.05)
# Two proportions: 40% vs 60%
pwr.2p.test(h = ES.h(0.6, 0.4), power = 0.80)