The table shown below comes from a study reported by Larry Bartels (2004), a political scientist. The table displays the mean and standard deviation (shown in parentheses) of annual real income growth from 1948 to 2001 for five family income levels. In this table, the 20th percentile is the lowest income level and the 95th percentile is the highest.

1. What do the means in the All Years column tell you about annual real income growth as related to income percentile?

2. What do the standard deviations in the All Years column tell you about fluctuations in annual income growth as related to income percentile?

3. What do the means in the Democratic President column and Republican Presidents column tell you about annual real income growth as related to income percentile and whether the president was a Democratic or a Republican?

4. Was the annual income growth rate more variable when a Democrat or when a Republican occupied the White House?

Democratic Republican Presidents Income Percentile All Years Presidents 2.63 1.58 .60 20th Percentile (3.90) (3.95) (3.65) 1.66 2.45 .93 40th Percentile (3.01) (2.97) (2.91) 1.32 1.86 2.46 60th Percentile (2.68) 2.37 (2.55) 1.60 (2.65) 1.97 80th Percentile (2.50) (2.55) 2.11 (2.43) 2.09 2.10 95th Percentile (2.96) 54 (3.30) 26 (2.67) 28