A scientist asked five of her dentist friends if they thought the new Brand X sugar dash free gum that she developed was effective. Four responded "yes." The scientist used the results to write a TV advertisement claiming that "4 out of 5 dentists prefer Brand X sugar dash free gum." Is this a valid inference? Explain.
Use pencil and paper. Explain all of the factors that are necessary for an inference to be valid.
Is the inference valid? Explain.