Artha Resources Corp CTMIF

RE: : RE: News impact

[ngobe]

Hi Jaemak,
I am glad you found that a bit amusing.  No offense taken. 
Just in case that was not enough, I thought of sharing with you and the board another scientific concept that can help interpret these reports - the concept of test sensitivity and specificity.  Every test has a sensitivity (a measure of how good it is in detecting what it is looking for vs. not detecting it at all).  It also has a specificity (a measure of how accurate it is in detecting what it is looking for vs. detecting something elst).  Generally the more sensitive a test is (lower false negatives)  the less specific it could be (higher false positives).  The best tests would therefore have high sensitivity and high specificity. But these test are generally not common and are often more invasive and expensive.  But combining tests (with different sensitivities and specificities) and looking for degree of agreement between them helps to draw better conclusion / assess probability of the find - "zoom in the target".  That is why these different tests are done.  And sometimes when a clear picture does not emerge more sampling or another test is done.  Of course the cheaper tests are done first (soil and rock chip sampling). But although they have good sensitivity (low false negative)  they tend to have low specificity (high false positive).  The size of sampling and its comparison with background levels improves the specificity (lower false positive).  But the test results need to be interpreted carefully - in the context of the local geology.  So if we have a wide area of surface grades and they are not that much different than the background levels, that may indicate that there is no good target (e.g., may be the surface material was carried by a glacier, or a river and does not correspond to a deep rock deposit) or may be that the deposit is widespread (i.e., disseminated).  Presence of other deposits / mines and understanding of their geology can help greatly.  And then one moves to more expensive and more invasive tests (e.g., different types of geophysical tests, trenching) which are generally more targeted, before doing the definitive but invasive and expensive drilling. 

Even though drilling is considered definitive (highly sensitive and specific) with reference to finding a targeted deposit, a single drill because of its narrow range has high sensitivity and low specificity and is thus a poor test with reference to delineating a deposit.  So multiple drilling is done at wide spacing first (high sensitivity and low specificity) to delineate a deposit leading to inferred catagory.  But for more definitive resource definition (in the M&I -> P&P catagories, i.e., higher specificity) closer space drilling is done. 

So test results (e.g., soil sampling) should be treated carefully with knowledge of their intrinsic sensitivity and specificty related to their target, reflecting probabilty, and interpreted in the context of other knowledge about the target including other types of tests.

GLTA