<p>The period prevalence has to be compared with the cross-sectional\r
prevalence. But both are statistical estimates and therefore\r
have confidence intervals.\r
-<b>For the cross-sectional prevalence we generally need information on\r
+<br>For the cross-sectional prevalence we generally need information on\r
the design of the surveys. It is usually not enough to consider the\r
number of people surveyed at a particular age and to estimate a\r
Bernouilli confidence interval based on the prevalence at that\r