Let's say that in some study, the original slope for the effect of weight on 60 second heart rate is a 1.615 bpm decrease in heart rate per 1 unit increase in weight (kg). This slope of 1.615 is our best estimate of the effect size (can be called the main effect or effect estimate), but as statisticians we know that it might be a little higher or lower. The standard error of this effect was 0.046 bpm/kg , which we can use to calculate a confidence interval around the main effect (a 95% CI ranges from 2 standard errors above the estimate to 2 standard errors below the estimate). After controlling for age, the new estimate of the main effect was 1.31. Was age a confounder