Explanation
The experiment shows that subjects had to predict where an image would appear on a screen, which was more frequently at the top than at the bottom. Despite this, their guesses were correct less than half the time, indicating that their strategy was not effective. The statement suggests that a simple strategy of always guessing 'top' would have yielded a better success rate.
A. This statement is speculative about the subjects' basis for guessing and does not necessarily follow from the given information.
B. This statement makes a comparative judgment about the effectiveness of guessing strategies that is not supported by the necessity of the experiment's results.
C. The experiment's result implies that the subjects did not detect a reliable pattern, but it does not definitively establish the non-existence of a pattern.
D. Given that the subjects guessed correctly less than half the time and the images appeared at the top most of the time, it follows that xsd the subjects must have guessed the bottom sometimes, leading to incorrect guesses.
An illustration might be: the subjects get it right 25% of the time (“less than half”) and the image appears at the top of the screen 90% (“usually”) and the bottom 10% (“occasionally”) of the time. If they guessed the top 100% of the time, they would have an accuracy of 90%. If they only guessed the bottom they would have an accuracy of 10%. Since their accuracy in this illustration is 25%, their wrong guesses cannot all be top. The number of errors when the image is on bottom is not sufficient to get to 25%. If the subject guessed all of the top images i.e. they never guess that the next image would be bottom incorrectly, they would instantly be at 90% accuracy.
First Example
#1 Top (Guess: Top)
#2 Top (Guess: Top)
#3 Bottom (Guess: Top)
#4 Bottom (Guess: Top)
#5 Top (Guess: Top)
Here the subject guessed correctly 60% of the time which violates the rule in the stimulus that he guessed correctly less than half the time, but he never incorrectly guessed the next image would appear at the bottom of the screen.
Second Example
#1 Top (Guess: Top)
#2 Top (Guess: Top)
#3 Bottom (Guess: Top)
#4 Bottom (Guess: Top)
#5 Top (Guess: Bottom)
Here Greg has guessed correctly 40% of the time, but the only way this was able to occur was by guessing bottom, but being incorrect. This occurs in roll #5
E. While this could be inferred as a more rational strategy, it is not a necessary truth that stems from the experiment's results and is not the only conclusion that could be drawn.
Based on the information provided, the statement that must be true is option D, which acknowledges that subjects sometimes guessed the image would appear at the bottom of the screen and were incorrect, given their overall success rate was less than 50%.