Final answer:
In Cal's vaccine experiment, the null hypothesis would be that 1. there is no difference in the effects of the vaccine and the placebo, as the null hypothesis proposes no effect of the independent variable.
Step-by-step explanation:
The null hypothesis in Cal's experiment, which studies the effects of a new vaccine where Group A receives the vaccine and Group B gets a placebo shot, would be: 1) There is no difference in the effects of the vaccine and the placebo.
The purpose of a null hypothesis is to provide a statement that there is no effect or difference as a result of the independent variable, in this case, the vaccine. Given the information that the placebo is designed to have no effect and is used to control for placebo effects in a double-blind experiment, it is clear that the null hypothesis is meant to demonstrate the lack of difference between the vaccine's effects and the placebo's lack of effects.
Additionally, in well-designed experiments like Salk's polio vaccine trial, a placebo is used to protect against bias and ensure any observed effects can be attributed to the vaccine. This is essential for maintaining the scientific integrity of the trial and ensuring reliable results.