Comparing Randomly Allocated Groups


Cibsuder a study to compare two antiobiotics for treating strep throat in children, amoxicillin and cefadroxil. At one clinic for this study, 23 children (who met the study entrance criteria and for whom consent was given) were randomly allocated into one of the two treatment groups. One concern is that age of the child might influence the effectiveness of the antibiotics. The ages of the children in each treatment group are given.

 Row    Age  Group
   1     14   AMOX
   2     17   AMOX
   3     11   AMOX
   4     10   AMOX
   5     11   AMOX
   6     14   AMOX
   7      9   AMOX
   8     12   AMOX
   9      8   AMOX
  10     10   AMOX
  11      9   AMOX
  12      9   CEFA
  13     14   CEFA
  14      8   CEFA
  15     10   CEFA
  16     13   CEFA
  17      7   CEFA
  18      9   CEFA
  19     11   CEFA
  20     16   CEFA
  21     10   CEFA
  22     12   CEFA
  23      9   CEFA

Calculate the mean and median for each of the two groups.

For the AMOX group the mean is

(14 + 17 + 11 + 10 + 11 + 14 + 9 + 12 + 8 + 10 + 9)/1 = 11.364

For the CEFA group the mean is

(9 + 14 + 8 + 10 + 13 + 7 + 9 + 11 + 16 + 10 + 12 + 9)/12 = 10.667

To obtain medians the two sets of data must be sorted. The median is then found in the center position.

For the AMOX group the median is 11

8 9 9 10 10 11 11 12 14 14 17

For the CEFA group the median is 10.

7 8 9 9 9 10 10 11 12 13 14 16

How do the two groups compare with respect to age?

They are quite similar -- at least via these measures.

Minitab (Computer-generated) Results

Descriptive Statistics

Variable   Group             N       Mean     Median     TrMean      StDev
Age        AMOX             11     11.364     11.000     11.111      2.693
           CEFA             12     10.667     10.000     10.500      2.640
Variable   Group       SE Mean    Minimum    Maximum         Q1         Q3
Age        AMOX          0.812      8.000     17.000      9.000     14.000
           CEFA          0.762      7.000     16.000      9.000     12.750