A psychologist puts a candle, matches, and thumbtacks on a table and brings participants into her lab to solve the following problem: attach the candle to the wall using only those materials. For half of the participants, the matches were spread out on the table next to the matchbox (the “Matchbox Empty” condition). For the other half of the participants, the matches were inside the matchbox (the “Matchbox Full” condition). Table $1$ shows the proportion of participants in each condition who correctly solved the problem (i.e., used the thumbtacks to attach the matchbox to the wall, then put the candle inside the matchbox). Table $1$ Matchbox Empty | Matchbox Full :-: | :-: $.84$ | $.46$ Suppose the psychologist does a follow-up experiment in which there are three groups instead of two. The first two groups are the same as in the original experiment. In the third group, participants come into the room and see thumbtacks, a candle, a matchbox full of toothpicks, and matches spread out on the table. Table $2$ illustrates the proportion of individuals in each group who correctly solved the problem. Table $2$ Matchbox Empty | Matchbox Full of Matches | Matchbox Full of Toothpicks :-: | :-: | :-: $.85 $| $.44$ | $.81$ **If the researcher measures the amount of time it takes to correctly solve the problem instead of measuring the proportion of participants who correctly solve the problem, what aspect of the study's design does she change?** [[☃ radio 1]]