A difference-in-differences research design seeks to exploit the differential effect of a specific treatment on a treatment group in order to mimic an experimental research design, but using observational data. Difference-in-differences calculates the effect of a treatment (an explanatory variable or an independent variable) on an outcome (a response variable or dependent variable). The difference-in-differences research design is viable if it can be empirically proven that other extraneous factors did not have an effect on the outcome. For example, the spread of Fox News and the effect of Fox News on Congress. In other words, much as a laboratory experiment a difference-in-differences approach has the ability, if done correctly and appropriately, to more adequately identify correlation and causality in observational data than other statistical techniques.
Another method utilized by researchers in order to establish correlation and causality while attempting to ensure a treatment effect independent of potential confounding factors is the use of serendipitous surveys. These are surveys which happen to be in the field when an event (treatment) takes place. For example, surveys measuring the American public’s attitudes towards terrorism which are in the field when the Department of Homeland Security issues a terror alert. Thereby, these surveys capture opinions on terrorism both before and after the alert was issued. The differences in opinion, sometimes captured utilizing a difference-in-differences research design, capture the effect of the treatment (the terror alert).
“Fox News anchor Bret Baier landed an exclusive joint interview with Donald Trump and Mike Pence on Friday. Unfortunately for everyone involved, the sit-down was taped just two hours before FBI Director James Comey sent his bombshell letter to Congress about Hillary Clinton-related emails.
“Because of its problematic timing, that interview, which aired during the 6 p.m. hour on the east coast, helped highlight the abrupt change in Trump’s rhetoric since news broke that the FBI would be reviewing additional emails found on Clinton aide Huma Abedin’s laptop in connection with the Anthony Weiner sexting case.
‘”The system is rigged when Hillary Clinton is allowed to run for president, because what she did is criminal,”‘ Trump told Baier Friday morning. ‘”The FBI rolled over and the Department of Justice rolled over.”‘ For extra emphasis, he added moments later, ‘”When she’s allowed to run for office, the FBI rolled over.”‘ Asked if he could lose this election without it being rigged, Trump declined to answer.”
“Those comments were strikingly different from the ones Trump made onstage at a rally in Manchester, New Hampshire just a few hours later. After telling his supporters about the new FBI probe and declaring, ‘”Perhaps finally justice will be done,”‘ Trump launched into his standard stump speech.
“When Trump got to his section about the increase in Obamacare premiums, he said, seemingly by force of habit, it was ‘”just one more way the system is rigged.”‘ But then he stopped himself. ‘”But with what I’ve just announced,”‘ he said, referring to the FBI news, ‘”it might not be as rigged as I thought, right? The FBI, I think they’re going to right the ship, folks. I think they’re going to right the ship. And they’re going to save their great reputation by doing so.”‘
Between Donald Trump’s taped interview with Bret Baier and his rally something occurred with softened his stance on the election being rigged against him. Given the short time span and the intervention which was Comey’s announcement it is fair to determine that announcement as the treatment. Furthermore, because of the short time span it is also fair to believe no other extraneous factors occurred which could have influenced Trump’s claims. A renewed FBI investigation disrupts Trump’s narrative that Hillary Clinton colluded with the FBI in order to prevent any potential criminal charges stemming from her use of a private email server and thereby allow her to run for president.
Additionally, Trump surrogate Rudy Giuliani, who has emphatically agreed with Trump’s claims of a rigged election in the past, appeared on CNN after Comey’s announcement and told Wolf Blitzer that now he doesn’t know “what the definition of rigged means.”
Comey’s letter was serendipitous because it just happened to occur between the taping of the Fox News interview and Trump’s rally. It also further elucidates the reasoning behind Trump’s claims of a rigged election.