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.
So although the issue of starting solids can be clouded by many opinions, delaying the start of solids until at least 4 months of age is pretty clear. 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.