The confidence intervals in the original paper [1] are surprisingly large:
>Results For Danish children born during the study period, 33% (95% CI, 0%-70%) of the increase in reported ASD prevalence could be explained by the change in diagnostic criteria alone; 42% (95% CI, 14%-69%), by the inclusion of outpatient contacts alone; and 60% (95% CI, 33%-87%), by the change in diagnostic criteria and the inclusion of outpatient contacts.
i.e., there's a 5% error probability that the "true" increase is smaller than 33% or larger than 87%. In other words, the "true" mean is somewhere in between 33% and 87%!
>Results For Danish children born during the study period, 33% (95% CI, 0%-70%) of the increase in reported ASD prevalence could be explained by the change in diagnostic criteria alone; 42% (95% CI, 14%-69%), by the inclusion of outpatient contacts alone; and 60% (95% CI, 33%-87%), by the change in diagnostic criteria and the inclusion of outpatient contacts.
i.e., there's a 5% error probability that the "true" increase is smaller than 33% or larger than 87%. In other words, the "true" mean is somewhere in between 33% and 87%!
[1] http://archpedi.jamanetwork.com/article.aspx?articleid=19196...