Final answer:
The dependent variable in Kiara's study is the speed of the marathon runners, operationally defined as their marathon completion time, which she hypothesizes might be affected by the type of chocolate consumed.
Step-by-step explanation:
Kiara believes that the type of chocolate consumed before a marathon could influence a runner's speed; thus, she is interested in establishing a relationship between these two variables. In this scenario, the dependent variable would be the speed of the marathon runners, which could be operationally defined as the time it takes for a runner to complete the marathon (usually measured in hours, minutes, and seconds). As a dependent variable, it is expected to change in response to the type of chocolate consumed, which is the independent variable. A solid operational definition must be specific, measurable, and based on observable data, such as using the exact finish times from official race results to quantify each runner's speed.
As the dependent variable, the runner's speed will serve as the outcome measure that Kiara will use to assess whether or not the type of chocolate has any effect. By comparing the marathon completion times across different groups of runners who have consumed different types of chocolate, Kiara could ascertain if there is a statistically significant difference in speeds, which might suggest a potential impact of chocolate consumption on marathon performance.