See, for instance, Gilbert (1980); problems with the assumptions of the theory and the difficulty of calibrating its parameters were pointed out as early as 1969 in Sauer's (1969) review of MacArthur and Wilson's book.
Considering the difficulties in calibrating these prices into specific joint probability distribution in practice, this study merely requires some fundamental descriptive statistics information of these bunker prices, including lower and upper bounds, means and covariances, which can be tangibly estimated from historical data.
Usually μ a and μ′ s are obtained from measurements of diffuse reflectance or of diffuse transmittance, and for the difficulties in calibrating the instrumentation measurements are usually available only in arbitrary units.
Therefore, despite the difficulty to calibrate and validate the model with empirical measurements, the maximum potential area at risk can be calculated more reliably.
But Mr Cameron has no option but to stick with it.The difficulty will be calibrating Britain's demands.
It is difficult to make a precise measurement, due to the difficulty in accurately calibrating the instruments used, and the problem of spatial coverage.
There are techniques which can potentially overcome this difficulty, including, for example, calibrating the distance of the TMS coil to each individual patient in accordance with the degree of atrophy [ 69].
There is no equivalent system for calibrating social difficulties, and therefore the decision to take the top 10% of SDI scores, as identified by the social work investigator, was made as the best available 'gold standard'.
"The protocol always calibrates difficulty to make up for increased mining power," he told the BBC, "so the speed at which people are finding blocks isn't going to go up by much no matter what".
In the pilot phase, 550 university students took the 20-item self-report can-do questionnaire and the 120 VELC Test® items, and then the item difficulty estimates were calibrated with the Rasch model separately for the reading and listening parts.
