For each of the experiments below, determine (1) which variable should be plotted on the Y axis and which on the X axis, (2) whether the researcher should use a line graph or a bar graph to present the data, and (3) how she should summarize scores on the dependent variable:
(a) a study of income as a function of age;
(b) a study of politicians’ positive votes on environmental issues as a function of the presence or absence of a wildlife refuge in their political district;
(c) a study of running speed as a function of carbohydrates consumed;
(d) a study of rates of alcohol abuse as a function of ethnic group.