One out of every ____ people in the United States is sixty-five years of age or older

You are running a simple study to determine if time of day affects student test performance. One

group takes a test at 9 AM, the other group takes the same test at 6 PM. During the afternoon session, the group seems distracted by the school band, which is practicing nearby, but the students finish the test on-time with no apparent problems. When you analyze the results, you find the morning group performed significantly better than the evening group. What should you conclude? A) The results are valid because researchers cannot always control factors like noise. B) The results are valid because the difference was significant. C) The results may be invalid because time of day affects mental performance. D) The results may be invalid because the band's noise was an extraneous variable.

Single mothers with a comfortable income who are in their 30s form a growing group in the United States. Children raised by such a single mother generally do not have behavior problems unless

a. mothers provide too many educational and recreational opportunities to the child. b. the child has a difficult temperament. c. stress levels are high and social support low. d. mothers were previously married and now divorced.