The reason for the lack of success

This lesson can be transferred to the gauging scale applied later on. A wide scale allows a high Trichostatin A but may not be workable. Therefore, it will be important to carefully determine the measurement scale for this investigation.
Woywode summarizes the difficulties of obtaining the qualitative information from key informants which may bias the evaluation of the SHS success in the following ways: key informant bias, endogeneity, simultaneity, unobserved heterogeneity, regression-to-the-mean-problem, and survival bias [27].
Below are some SHS related examples of these difficulties, taken from the literature:
2.1.1. Key informant bias
Key informants may fail to provide information on past dependencies compared to their situation today [28]. SHS Users may fail to remember living conditions before the implementation of their SHS. Therefore, the evaluation of the SHS services may be biased.
2.1.2. Endogeneity
Independent variables are influenced by variables which have not readily been accessible [29]. At first sight, the price of SHS components seems to be an independent variable. But the price may be influenced by difficulties and hidden costs of importation. Information on axillary buds influences is often difficult to access.