Professor Johnston has found a strong positive correlation between wearing neckties and the frequency of strokes (r = 0.89). He thinks that the necktie reduces blood flow to the brain, preventing the brain from receiving enough oxygen. Professor Johnston and his associates claim to have proven that wearing neckties causes strokes. What error has Professor Johnston made?
a. An r = 0.89 is not a very large r-value.
b. Professor Johnston is drawing a causal conclusion from correlational findings.
c. Not everyone who wears a necktie wears it very tight.
d. Professor Johnston should know that there are other ways for blood to reach the brain.
Question 2
If we calculate a correlation coefficient and we find that there is a relationship between the two variables, we
a. know that the data must be interval or ratio.
b. know, without referring to the study, that a correlational design was used.
c. can conclude that changes in one variable cause changes in the other variable.
d. cannot conclude that changes in one variable cause changes in the other variable.
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