# problem-9.13

problem-9.13 After massaging the data, a glimpse at a contingency table shows us that there appears to be some dependency between the variables. This is borne out by the tiny p-value returned by chisq.test().

    > aq = airquality[complete.cases(airquality),]
    > attach(aq)
    > te = cut(Temp, quantile(Temp))
    > oz = cut(Ozone,quantile(Ozone))
    > table(te,oz)
               oz
    te          (1,18] (18,31] (31,62] (62,168]
      (57,71]   15      9       3       0
      (71,79]   10     10       7       1
      (79,84.5]  4      6      11       5
      (84.5,97]  0      0       6      22
    > chisq.test(te,oz)

            Pearson's Chi-squared test

    data:  te and oz
    X-squared = 76.31, df = 9, p-value = 8.713e-13