The term "experiment" usually implies a controlled experiment, but sometimes controlled experiments are prohibitively difficult or impossible. In this case researchers resort to natural experiments or quasi-experiments .  Natural experiments rely solely on observations of the variables of the system under study, rather than manipulation of just one or a few variables as occurs in controlled experiments. To the degree possible, they attempt to collect data for the system in such a way that contribution from all variables can be determined, and where the effects of variation in certain variables remain approximately constant so that the effects of other variables can be discerned. The degree to which this is possible depends on the observed correlation between explanatory variables in the observed data. When these variables are not well correlated, natural experiments can approach the power of controlled experiments. Usually, however, there is some correlation between these variables, which reduces the reliability of natural experiments relative to what could be concluded if a controlled experiment were performed. Also, because natural experiments usually take place in uncontrolled environments, variables from undetected sources are neither measured nor held constant, and these may produce illusory correlations in variables under study.
So, you have done your experimentation, and recorded your results – now it’s time to gather your data.
In 2003, Darfur rebels took up arms against the Sudanese government. Khartoum and allied militia groups responded with a brutal counter-insurgency campaign. [fn] Crisis Group Africa Briefing N°14, Sudan’s Other Wars , 25 June 2003; Crisis Group Africa Reports N°76, Darfur Rising: Sudan’s New Crisis , 25 March 2004; N°80, Sudan: Now or Never in Darfur , 23 May 2004; N°83; Darfur Deadline: A New International Action Plan , 23 August 2004. Hide Footnote Beijing’s close economic and political ties with Khartoum, particularly via the oil industry, led to Western accusations that it was bankrolling and protecting a genocidal regime. [fn] China invested billions of dollars in Sudan’s oil industry and imported 60 per cent of Sudan’s crude oil before 2011. China became Khartoum’s largest arms supplier around 2004 and helped Sudan build its domestic arms manufacturing industry. It was responsible for more than 70 per cent of total small arms and light weapons (SALM) transfers to Sudan between 2001 and 2008. Beijing also was seen as Khartoum’s protector in the UN Security Council. Crisis Group Report, China’s New Courtship in South Suda n , op. cit., p. 20; “Arms, Oil, and Darfur: The Evolution of Relations between China and Sudan”, Small Arms Survey, Sudan Issue Brief , Number 7, July 2007; “Supply and Demand: Arms Flow and Holdings in Sudan”, Small Arms Survey, Sudan Issue Brief , Number 15, December 2009. Hide Footnote Activists called for a boycott of the 2008 Beijing Olympics, China’s purported coming-of-age show. Denying any responsibility for the Darfur war, yet fearing a public relations crisis, Beijing sought to “clean up the mess”. [fn] The foreign ministry argued the Darfur issue dated back to 1916, when it was under British control, and said: “It would be too far-fetched to blame China”. “外交部部长助理翟隽就苏丹达尔富尔问题举行中外媒体吹风会 [“Assistant Foreign Minister Zhai Jun Briefs Chinese and Foreign Media on the Darfur Issue in Sudan”], press release, Chinese foreign ministry, 12 April 2007. Crisis Group interview, Chinese scholar on Africa studies, Shanghai, March 2016. Hide Footnote In May 2007, it appointed Liu Guijin, a seasoned diplomat, as its special representative for African affairs and the Darfur issue. [fn] “China appoints Darfur post”, Associated Press, 10 May 2007. Hide Footnote
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