In social science research, "highest education level attained" would refer to the most advanced grade or degree achieved by an individual-for some individuals, it may be a grade in grade school, and for other individuals, it may be a Bachelor' s Degree, a Master' s Degree, or Ph. D. (which is considered the highest education level). A recent study has shown a strong correlation between highest education level attained and proficiency in chess. Another result, studied at many points throughout the 20th century, shows a marked positive correlation between highest education level attained and income level. Assuming the statements above are true, what conclusion can be drawn? ["An individual's proficiency at chess rises consistently during that individual's years of school, and levels off once that individual has finished her years of formal education.", 'If Jane has a Ph. D. , and Chris has not finished his undergraduate degree, then Jane will usually beat Chris in chess.', 'It is possible that a person who has attained only a sixth grade level of education could earn more than a person who has a Ph. D.', "If one practices chess enough to raise one's proficiency, one has a good chance of raising one's income level."]