A limitation of this prospective study is the time elapsed since the period when data were collected (1998, 2000): there is a risk that the case mix of patients in the PICU has changed over this period.
The university branch where the research was conducted was experimenting with a synchronous course for the first time during the same time period when data was collected.
For the countries shifting from ICD-9 to ICD-10 during the study period, we limited our analyses to the period when data were recorded under ICD-10.
The estimated date of conception was used to estimate the last menstrual period when data on last menstrual period were missing or considered extreme (> 44 weeks before the birth date).
The transferability of the study was strengthened through descriptions of the settings of the intervention, the number of participants in the study, the data collection methods and the time period when data was collected.
Pollution levels during the winter of 2004 were generally lower than previous years [ 18], with the majority of high pollution nights occurring during the school vacation period, when data was not being collected.
However, the estimated bias may have been greater, had account been taken of the possibility of subjects taking up smoking later in the follow-up period, when data were not collected.
But we won a $100,000 early stage challenge from Nvidia during a period when big data was hot". Over the last few years MapD has raised more money.
Fire activity (inferred from the frequency of charcoal peaks) averaged 18 fire episodes/1000 years from 3800 to 2125 cal year BP, and increased from 16 fire episodes/1000 years at 2125 cal year BP to 22 episodes/1000 years at 750 cal year BP, a period when the pollen data suggest that steppe vegetation yielded to increasing patches of forest cover.
Overall, a federal survey gauging Americans' health behaviors has found that obesity among children in the United States has remained flat -- at around 17% -- in 2003-2004 and 2011-2012, the periods when data were collected.
As a result of all the potential difficulties, historical exposure is often ignored and analysts look for associations with exposures in recent periods when data are complete.
