A student wants to determine how well tulips will bloom at high temperatures. She knows they bloom well at room temperature, so she sets up groups at higher temperatures: 80°F, 90°F, and 100°F.

A control group would keep tulips at room temperature, where they are known to bloom well, so the student could compare them with the groups at 80°F, 90°F, and 100°F. Since the design includes only higher-temperature groups and no room-temperature comparison group, it lacks a control group.

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