Problem: In studies that implement an intervention, which two statements about fidelity of an intervention are true? Fidelity refers to the degree to which a treatment is implemented as intended. Lack of treatment fidelity decreases internal validity. Deviations in an intervention protocol support intervention fidelity and the ability to detect a change in the outcome of interest. The higher the fidelity of an intervention, the lower the confidence that changes in the outcome of interest are due to the intervention. Training personnel who provide the intervention is not needed to support fidelity. Lack of fidelity can reduce the effectiveness of an intervention.