In a headline that reads, "A chat on the porch reduces transphobia", the Pacific Standard summarizes a recent paper in the prestigious journal Science. According to the article, people who have an empathic, perspective-taking conversation with a canvasser end up becoming more supportive of transgender people over time.
Here are some descriptions of the study, as described by the journalist:
The new study was conducted in Miami-Dade County, Florida, which, in 2014, passed an ordinance protecting transgender people from discrimination in housing and employment. It began with a “baseline survey,” in which 1,825 voters were asked their views on a variety of issues, including that ordinance.
Canvassers subsequently came to the door of 501 of the surveyed families. Half of them initiated a conversation about the importance of recycling; the other half talked about transgender rights. (Fifteen of the volunteers who went door to door to talk about the latter issue were transgender, and identified themselves as such; another 41 were not.) Note: the Science article specifies that people were randomly assigned to these conditions.
During the conversations, the canvassers encouraged people “to actively take transgender people’s perspectives.” Specifically, they “first asked each voter to talk about a time when they themselves were judged negatively for being different.” They then “encouraged voters to see how their own experience offered a window into transgender people’s experiences.”
Follow-up online surveys were conducted three days, three weeks, six weeks, and three months after the visit. They revealed that...voters who discussed the experiences of transgender people “were considerably more accepting” of such individuals than those who talked about recycling. (Beforehand, the transgender-acceptance scores of both groups were roughly equal.)
(Last year, a similar study arguing that personal canvassing increased support for gay marriage made the news because the data had been fabricated. This study was conducted by two scientists who helped uncover the fraud in the previous study.)
a) This is an experimental study, rather than a correlational one. Why? What are the study's main variables?
b) What kind of experiment is this? Pretest posttest? Posttest only? Concurrent measures? Repeated measures? What are its IV and DV? How many levels are there in the IV (and what are they?)
c) Can the results support the claim in the headline, that "A chat on the porch reduces transphobia"? Apply the three criteria for causation.
d) Can we rule out internal validity threats such as attrition, history, selection, or maturation? Why or why not?