Confidence interval for the slope
The slope of the least squares line, b1, is a good estimate of the normal linear model's slope, β1, and the error in this estimate has a normal distribution,
Tourist arrivals in Hawaii
Warning: These data are observational, not experimental, so it would be wrong to conclude from these data alone that radiation seepage from the plant caused the increase in deaths. The 'exposure index' depends on distance down the Columbia River from the plant (among other factors) and there could be other environmental changes downstream that also affect cancer deaths.