d <- read.csv("two_groups.csv")
t <- d$value[d$group == "treated"]; c <- d$value[d$group == "control"]
g <- factor(d$group); dev <- abs(d$value - ave(d$value, g))           # Levene, mean-centred, as SPSS uses
lev <- anova(lm(dev ~ g))
s <- t.test(t, c, var.equal = TRUE); w <- t.test(t, c)
cat(sprintf("Levene's test (mean-centred): F = %.2f, p = %.3f\n", lev$`F value`[1], lev$`Pr(>F)`[1]))
cat(sprintf("Equal variances assumed (Student): t = %.2f, df = %.0f, p = %.3f\n", s$statistic, s$parameter, s$p.value))
cat(sprintf("Equal variances not assumed (Welch): t = %.2f, df = %.2f, p = %.3f\n", w$statistic, w$parameter, w$p.value))