Dr. Math was interested in how children learn multiplication. Dr. Math recruited 54 second-graders who had not yet been taught how to multiply numbers to participate in a study. Dr. Math was curious as to whether different methods of instruction would lead to better mastery of the subject. Some students read a chapter on multiplication from their textbook. Other students watched a video of cartoon characters explaining multiplication. A third group of students were taught multiplication by a teacher. In all conditions, participants spent 30 minutes learning the fundamentals of multiplication with one of these three methods of instruction and were then given the same 15-question multiplication test. The number of questions answered correctly was recorded and was used as a measure of multiplication ability. Dr. Math obtained the results in the table below and concluded that the math instruction type affected learning of multiplication. Textbook Video Teacher Number of problems 8 correct 10 13 1. Identify and clearly label the independent variable(s), dependent variable(s), and a control variable in this study.
2. Explain how Dr. Math's study meets the covariance rule for causality AND the temporal precedence rule for causality.
3. Write a question that you would ask to interrogate the internal validity of Dr. Math's study and explain why this questions addresses internal validity.

experiments.

surveys.

questionnaires.

interviews.

case studies.

participant and non-participant observation.

observational trials.

studies using the delphi method.

buildings

explanation:

question - in 1827, john walker, a druggist in a small english town, tipped a splint with sulphur, chlorate of potash, and sulphid of antimony, and rubbed it on sandpaper, and it burst into flame. the druggist had discovered the first friction-chemical match, the kind we use to-day. it is called friction-chemical because it is made by mixing certain chemicals together and rubbing them. although walker's match did not require the bottle of acid, nevertheless it was not a good one. it could be lighted only by hard rubbing, and it sputtered and threw fire in all directions. in a few years, however, phosphorus was substituted on the tip for antimony, and the change worked wonders. the match could now be lighted with very little rubbing, and it was no longer necessary to have sandpaper upon which to rub it. it would ignite when rubbed on any dry surface, and there was no longer any sputtering. this was the phosphorus match, the match with which we are so familiar. according the paragraph what was the benefit of the new phosphorus match? it burst into flame when rubbed on sandpaper. it was made by mixing chemicals. it could be ignited on any dry surface. it threw fire in all directions.

answer - matches required natural chemicals