Dr. DeVries is interested in measuring how practice in problem solving affects this ability. The population of interest is high school seniors, and the sample consists of students who attend an exclusive college preparatory school. Half of the sample receives practice in solving particular types of problems, while the other half does not. Both groups take the same problem-solving test. Which of the following might best explain why Dr. DeVries may not be able to generalize his findings? A) He is not taking into account how the scores on the test might deviate from one another.
B) His data may be positively skewed.
C) He should have conducted his experiment in a lab instead of a natural setting.
D) His sample is not representative of the population.

Option D) is correct

Explanation:

Dr. DeVries is interested in measuring how practice in problem solving affects this ability. The population of interest is high school seniors. However, the sample consists of students who attend an exclusive college preparatory school out of which half of the sample receives practice in solving particular types of problems, while the other half does not receives practice in solving those types of problems. Now groups take the same problem-solving test. But  DeVries may not be able to generalize his findings as the sample is not representative of the population.

the answer is solomon northrup. he was a free-born african american, abolitionist and professional violinist that was drugged, kidnapped and sold as slave in 1841 and remained in captivity until 1853 where he regained his freedom with the of the then-governor of new york, washington hunt. he wrote and published his memoirs "twelve years a slave" in 1853, and in this text, he tells the story of his escape thru one of louisiana's swamps (the great pacoudrie swamp) in which he ended up covered in green slime from crossing the surface of the dead water.