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 current debate is then whether babies should start at 4 months or 6 months. Some health care groups say you can start solids at 4 months while others strongly encourage waiting until closer to 6 months of age. The thing we need to realize is that your baby's development isn't like a light switch - suddenly she is now ready for solid food when the day before she was not.