
84 Data Analysis and Statistics for Geography, Environmental Science, and Engineering
For example, go to Continuous distributions|Normal distribution and use the quantiles option
(Figure 3.24) to obtain quantiles given probabilities. We can determine the quartiles or quantiles for
probabilities 0.25, 0.50, 0.75 (see Figure 3.25). We get the result in the output window
> qnorm(c(.25,.50,.75), mean=0, sd=1, lower.tail=TRUE)
[1] -0.6744898 0.0000000 0.6744898
FIGURE 3.23 Rcmdr distribution menu items for continuous distributions.
FIGURE 3.25 Calculating quartiles for the normal distribution.
FIGURE 3.24 Selecting quantiles option for normal dist