An experimenter is interested in the influence of taking a one-semester-long test preparation course on performance on the Scholastic Aptitude Test (SAT). She contacts high school students who have and who have not taken the course and compares their scores on the SAT exam. She finds that the students who have taken the course score significantly higher on the test. Which of the following represents the principal threat to the internal validity of this experiment?
a. Regression to the mean
b. Maturation
c. Selection
d. Attrition
Question 2
An experimenter is interested in the influence of taking a one-semester-long test preparation course on performance on the Scholastic Aptitude Test (SAT). She contacts high school students who have and who have not taken the course and compares their scores on the SAT exam. She finds that the students who have taken the course score significantly higher on the test. The appropriate statistical test is
a. descriptive statistics.
b. Pearson correlation.
c. chi-square.
d. one-way ANOVA.
The Wug Test
The Mantoux tuberculin skin test. Positive reaction.
Brush off front to finish. Long brushing strokes from head to feet to finish.
Brush off the back. Apply several long brushing strokes from head to hips to finish the session.
Three Pieces of the Long-Term Weight-Loss Puzzle Diet
Greater Long-nosed Tree Shrew (Tupaia tana), Borneo and Sumatra.