Final answer:
The number of dependent variables in an experiment is not specified, but each example listed includes both an independent variable and a dependent variable, with control variables playing a critical role in establishing causation.
Step-by-step explanation:
In the context of the video entitled "Independent and Dependent Variables" posted on Moodle, the number of dependent variables described and measured is not explicitly stated in your question. However, typically in an experiment, researchers aim to manipulate one independent variable and measure its effect on one dependent variable, although it is possible to have multiple dependent variables. For instance, in the given examples from your question, the independent variables are factors such as age, number of family members, and higher education, while the dependent variables include fatalities, grocery bill, insurance premium, utility bills, and crime rates.
It is important to identify the control variables, which are kept constant to ensure that any observed effect on the dependent variable is indeed due to the independent variable. Control variables are critical for establishing causation, as they help to isolate the relationship between the independent and dependent variables.