BCal help system: The Tutorial

Step C4: Viewing posterior density plots for individual parameters

We now see a plot of the posterior probability distribution for alpha 2. The densest area of the plot shows the most likely calendar dates for the event represented by this parameter. From the plot we can see that the most likely calendar dates are in the range 600-10 cal BP. Recall that we provided absolute a priori chronological information that beta 2 is exactly 9 cal BP (1941 AD). This means that all dates at this site are constrained to be earlier than 9 cal BP. The obvious consequences of this can be seen at the right-hand end of our plot.

As well as viewing the posterior probability distribution as a plot, we can view the distribution as a highest posterior density (HPD) region. To do this, we must move back to the format and parameter selection page by selecting "Back" (for the tutorial you should select "Next" to continue).

Note: The smoothness of the graph depends partly on the bin widths you set when you submit the job for calibration. If you want smoother (or less smooth) results you need to resubmit your job, setting the bin widths appropriately.