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Group Purpose


A Scientist decides to test the effect the addition of giberellic acid has on root growth in newly planted pea shoots. She sets up an experiment where she will test various concentrations of giberellic acid solution. She sets up five groups of twenty-five plants each. Four of the groups are watered daily with various concentrations of giberellic acid solution, the fifth with water without any additives. The length of the main root was measured every 3 days in each plant and the average of each group was recorded. The results are summarized in the data table below:

$$ \text{ Length of Main Root (cm):} $$

Group # Conc of Gib. Acid (ug/ml) Day 3 Day 6 Day 9 Day 12 Day 15
1 0 2 2.2 2.5 2.8 3.1
2 10 2.1 2.5 2.9 3.3 3.5
3 20 1.9 2.7 3.0 3.5 3.9
4 30 2.2 2.9 3.3 3.7 4.1
5 40 2.0 2.3 2.4 2.4 2.5

What is the purpose for Group #1 being included in this study?


It gives data as to what happens when a high concentration of giberellic acid is added to the water.


It is the main variable used in the experiment.


It is used to compare the number of leaves between groups.


It is used as a basis of comparison for the other groups.