In a(n) ______, the scientist deliberately changes one variable and measures the change in some other variable

Which of the following statements about lead exposure in young children is true?

a. The environment of inner-city, low-income children in the United States still contains lead. b. Lead does not appear to harm the developing brain in a permanent way. c. In one five-year longitudinal study, lead levels in young children were brought down using nutritional and mineral treatments, and cognitive deficits disappeared. d. As long as there is no lead found in the home, children are safe from lead exposure.

What is a problem with current tests of "emotional intelligence"? a. For many items, no one is sure what the correct answer is

b. Many people get far higher scores on the test than other people do. c. Many items are so complicated that highly educated people have an unfair advantage. d. The tests require expensive equipment that is unavailable in most places.