Sentence examples for difficult to test by from inspiring English sources
Elastic constants are important for internal stress measurement, yet the value for thin films is difficult to test by mechanical methods.
We excluded the interaction term because it was not significant, and it is difficult to test effect modification by HFE genotype.
Unfortunately, because this species is becoming so rare, it is extremely difficult to test this possibility directly by comparing insular and continental Egyptian vulture populations of differing densities.
However, it has been difficult to test this hypothesis directly by following iACs and dACs during the earliest stages of IPL formation, partly because there are no known markers to distinguish iACs and dACs.
It is largely driven by speculation and difficult to test empirically at present (Kitchin 2002; Pickrell and Oehme 2002).
While it is difficult to test this relationship on a country level, it may be possible by looking at indicators of income inequality, e.g., GINI index.
While this "germline codon" hypothesis is supported by various lines of evidence, it has been difficult to test.
