Given the long latency of this disease, the unclear role of airborne transmission in M. bovis TB (13 ), and the fluid population dynamics of the San Diego region, however, the true population at risk and what might be behind the trends observed are difficult to describe.
The health risks associated with occupant exposure to the concentrations we observed are difficult to calculate because of the few studies that have reported bacterial aerosol concentrations in indoor air (IOM 2004) and the resultant lack of epidemiologic data available for typical indoor environments.
Since it is difficult and often impossible to carry out experiments and since the uncontrolled phenomena economists observe are difficult to interpret (owing to the same causal complexity that bothered Mill), it is hard to judge whether a particular theory is a good basis for predictions or not.
Due to the variation observed, it is difficult to draw any conclusions.
Given that climate change cannot be directly experienced or straightforwardly observed, it is difficult for individuals to link local weather events and climate change.
While statistically significant differences were observed, it is difficult to translate the small magnitude of score improvement to actual staff motivation.
Our experimental results suggest, however, that inference of migration from observed data is difficult, even with a full-likelihood model.
While the majority of the initial glycemic effect was maintained over the 3 years of treatment, a gradual upward trend in HbA1c and FPG concentrations was observed that is difficult to interpret in the absence of a comparator arm.
As no significant differences in the basic characteristics of patients with blood type A and non-A types were observed, it is difficult to explain the effect of ABO blood groups based on this point.
