The Florida Scientist (Summer/Autumn 1991) reported on a study of the feeding habits of sea urchins. A sample of 20 urchins was captured from Biscayne Bay (Miami), placed in marine aquaria, and then starved for 48 hours. Each sea urchin was then fed a 5-cm blade of turtle grass. Ten of the urchins received only green blades, while the other half received only decayed blades. (Assume that the two samples of 10 sea urchins each were randomly and independently selected.) The ingestion time, measured from the time the blade first made contact with the urchin€™s mouth to the time the urchin had finished ingesting the blade, was recorded. A summary of the results is provided in the following table:

In the field may find it more profitable to selectively graze on decayed portions of the leaves.€ Do the results support this conclusion?

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Green Blades Decayed Blades 10 Number of sea urchins Mean ingestion time (hours) Standard deviation (hours) 10 3.35 .79 2.36 .47