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.
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. 7 to 12 months: Babbles with greater diversity, making new sound combinations and intonations.