Aresearcher interested in establishing that there is a causal relationship between variables is most interested in validity. artificial linear internal construct

He is more interested in the Internal Validity. Internal validity is of significate importance in scientific studies, and indicate if the variable analyzed is the cause of the effect obtained in the research, or whether the effect obtained is the product of another variable. For example, in an investigation analyzing the effect of anxiety on test results, care should be taken not to study other effects that may affect test results, such as fatigue or lack of study.

some of these parties must join together to obtain the power to govern

Explanation:

there is high competition among these parties and high partisan politics, dividing voters among the parties almost equally. This will hinder full representation as one party will likely not get the full support and power to govern all. This is why there is need for a coalition party that would bring most or all parties together to get more support from the public and govern more effectively without resistance from opposing parties