2.3 K-Sample Data

Like 2-sample data , but comparing k>2 treatments. Here is an example:

Track etch devices were under consideration as an inexpensive way to measure low-level radiation in homes. An experiment was done to study the usefulness of such devices. Measurements were taken on four different types of such devices: Filter, Membrane, Open Cup and Badge. Twenty devices of each type were put in a chamber and subjected to constant radiation. The amount of radiation measured by each device was recorded.

The data are given in the following table:

       FILTER        MEMB             CUP               BADGE

       26            45               36                21
       21            33               34                23
       16            26               33                27
       28            46               29                29
       27            25               30                24
       19            32               36                26
       21            33               28                27
       26            22               34                26
       25            30               34                24
       16            26               33                25
       20            37               33                31
       25            34               29                28
       25            44               28                30
       21            43               27                30
       23            35               27                31
       26            38               30                29
       21            38               29                29
       23            45               28                29
       17            39               31                30
       25            39               27                28

Before you start your MINITAB session, copy the data file into your account:

    cp /afs/acpub/project/sta215/radon.data  radon.data

Then start a MINITAB session

    minitab

You can read the data into your MINITAB session by

    read 'radon.data' c1 c2 c3 c4  
    names c1='FILTER' c2='MEMB' c3='CUP' c4='BADGE'

The first command reads the data file into the columns c1-c4. The second command assigns meaningful names to the data columns.

Question 2: Which type of data model does this experiment represent?

Click here for an answer .

Question 3: How do the four devices compare? The following MINITAB commands will be helpful in answering Question 3:

    dotplot 'FILTER' 'MEMB' 'CUP' 'BADGE'

Click here for an answer .

Again, to leave MINITAB, type

    stop

The k-sample boxplot at the begiining of this page was created using S-plus.