Karlan, Appel, Duflo and Banerjee tackle that question through randomized control trials (RCTs).

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In the double-blind, randomized control trial, half the women got tenofovir gel and half got a placebo.

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While high-end evaluation methods like randomized control trials (RCTs) are the surest means of determining what interventions in fact cause certain outcomes, they are also time-consuming and costly and beyond the means of many, if not most, mainstream nonprofits.

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These are the gold standard randomized control trials or intervention studies, in which a control group consuming soda is monitored for weight gain over time against a group which stops drinking soda (and all other dietary and lifestyle factors are controlled for).

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The investigators are now conducting a randomized, controlled clinical trial of RAGE Control in the outpatient clinic at Boston Children's that adds a cooperative component.

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Similarly, in patients who have just had bypass surgery, the group randomized to an ICD did not have better survival than the control group.

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Both projects were rigorous randomized trials, comparing kids who got pre-K benefits with a control group that didn't.

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The gold standard for testing medical treatments is the randomized trial, in which patients are randomly assigned to a treatment or control group to spread patient differences evenly and avoid bias in results.

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