Final answer:
The statement '4 out of 5 doctors prefer a certain medication for a headache' is an d. appeal to authority, which is used to imply that the medication is effective because most doctors prefer it, thereby using the doctors' professional authority to validate the product.
Step-by-step explanation:
The claim that "4 out of 5 doctors prefer" a certain medication for a headache is an example of an Appeal to Authority. This type of statement suggests that because most doctors prefer it, the medication must be effective. The speaker is leveraging the presumed authority of medical professionals to support their product without presenting direct evidence of its efficacy.
An Appeal to Authority is often used in advertising and propaganda to persuade the public. It implies that the opinion of an authority figure, such as a doctor, is more valid than others and should be trusted. However, this does not necessarily mean the information is factually correct; it is a tactic used to encourage people to accept a claim without the need for further proof or scientific evidence.