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.
5 to 6 months. Practices intonation by making her voice rise and fall, often in response to baby talk and your facial expressions. Red flag: If your child isn't making vocal sounds by the time she's 6 months old, talk with her doctor. Babbles with greater diversity, making new sound combinations and intonations.