Does daily cardio exercise make subjects perform better on tests of intelligence? A study was conducted in which the daily habits of 45 college students were documented, focusing on the number of hours spent on exercise in a week. After a week, the subjects were given a computer-based intelligence test on which they receive a score on a 0 to 100 point scale. Their scores were compared with how many hours they spent exercising that week.

Select all that apply.
Choose at least one answer.
1 This is best described as an observational study.
2 The response variable is the score on the computer-based intelligence test.
3 The explanatory variable is the number of hours exercised during the week.
4 The response variable is the number of hours exercised during the week.
5 The explanatory variable is the score on the computer-based intelligence test.
6 This study is best described as an experiment.