An experimental group is the group in an experiment that receives the variable being tested. One variable is tested at a time. The experimental group is compared to a control group, which does not receive the test variable. In this way, experimental groups are used to find answers in an experiment.
1 At around 9 months of age, babies begin to pull themselves up to a standing position. 2  By 10 months of age, a baby should be able to grasp objects with thumb and forefinger.
The age when infants begin showing a preference for color is at about 12 weeks old. Generally, children prefer the colors red/ pink and blue, and cool colors are preferred over warm colors. Purple is the color favored more by girls than by boys. Color perception of children 3â5 years of age is an indicator of their developmental stage.