It is thought that stress may increase susceptibility to illness through suppression of the immune system. In an experiment to investigate this theory, 48 rats were randomly allocated to four treatment groups: no stress, mild stress, moderate stress, and high stress. The stress conditions involved various amounts of restraint and electric shock. The concentration of lymphocytes (cells/ml × 10-6) in the peripheral blood was measured for each rat, with the results given in the accompanying table.4 Calculations based on the raw data yielded SS(between) = 89.036 and SS(within) = 340.24.

(a) Construct the ANOVA table and test the global null hypothesis at α = 0.05.
(b) Calculate the pooled standard deviation, Spooled.

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No Mild Moderate High stress stress 4.84 2.42 stress 3.98 3.91 stress 6.64 2.77 2.92 1.45 12 12 12 12