# extract coefficients
coefs <- data.frame(coef(summary(m3)))

# get p-values from the t-distribution using the t-values and approximated
# degrees of freedom
coefs$p.KR <- 2 * (1 - pt(abs(coefs$t.value), df.KR))
coefs

# use normal distribution to approximate p-value
coefs$p.z <- 2 * (1 - pnorm(abs(coefs$t.value)))
coefs