Descriptive Statistics

THIS DATASET IS AVAILABLE IN BBVISTA EXERCISES FOLIDER. YOU CAN USE IT TO REPLICATE THE EXAMPLE

Selected output for males is shown in Figure 5.13. The Descriptives table for males: the mean number of hours worked last week is 45.49; the median is 43.50. The standard deviation is 15.206, the range is 88, and the IQR is 12.5,16 which is quite narrow compared with the range or standard deviation.

Although not displayed here, the mean number of hours worked last week for females is 38.62; the median is 40. The standard deviation is 12.346, the IQR is 8, and the range, 79— values somewhat smaller than those for males. The variation in the number of hours worked last week is also slightly smaller for females than those for males. Explore displays separate box plots for males and females in the same window for easy comparison ( Figure 5.14).

The SPSS box plot summarizes the distribution: The solid dark line in the middle is the value of the median. The width of the shaded box ( in color on the screen) is the IQR ( 12.5 for males, 8 for females). Note that SPSS only extends whiskers from the box edges to 1 ½ times the box width ( the IQR). If there are additional values beyond 1 ½ times the IQR, SPSS displays the individual cases. Those that are somewhat extreme ( 1 ½ to 3 box widths from the edge of the box) are marked with an open circle; those considered very extreme ( more than 3 box widths from the box edge) are marked with an asterisk.

The box plot shows us that variability in hours worked last week is smaller for females than for males. Note that the box is substantially smaller for females than for males. The IQR for males runs from 40 to 52.5, while the IQR for females runs from 35 to 43. Both genders have outlying cases beyond the edge of the whiskers.