The public debt in the U. S. (in billions of dollars) has grown as follows: Year Spending (in billions of dollars) 1910 2.65 1920 25.95 1930 16.19 1940 42.97 1950 257.36 1960 290.22 1970 389.16 1980 930.21 1990 3233.31 2000 5674.18 2010 13529.21 a. Give a scatter-plot and residual plot of the data.

Ascientist studied a population of workers to determine whether verbal praise and/or tangible rewards affect employee productivity. in the study, some workers were offered verbal praise, some were offered tangible rewards (gift cards, presents, and some were offered neither. the productivity of each participant was measured throughout the study by recording the number of daily tasks completed by each employee. which inference might the scientists make based on the given information? a.) the number of daily tasks completed by each employee may influence the dependent variable, which is whether the employee receives verbal praise, tangible rewards, or neither. b.) verbal praise and/or tangible rewards may influence the independent variable, which is the number of daily tasks completed by each employee. c.) verbal praise and/or tangible rewards may influence the dependent variable, which is the number of daily tasks completed by each employee. d.) the dependent variables, which are verbal praise and tangible rewards, may influence the number of daily tasks completed by each employee.