EXAMPLE 20 Newborn babies and a heartbeat: An experimental study

A psychologist wanted to test whether the sound of a human heartbeat would help newborn babies grow. A baby nursery at a hospital was set up so that the sound of a human heartbeat could be heard throughout the nursery. The heartbeat sound was played in the nursery for a large batch of newborn children, who were then weighed to determine their weight gain after four days in the nursery. Later, a second batch of children occupied the nursery, but no heartbeat sound was played. These children were also weighed after four days in the nursery. Babies were randomly placed into the two groups. Identify the following:

  1. The subjects
  2. The predictor variable
  3. The treatment
  4. The response variable
  5. The control

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Solution

  1. The babies were the subjects of this experimental study.
  2. The predictor variable is whether or not the heartbeat sound was played in the nursery.
  3. The treatment is the sound of the human heartbeat.
  4. The response variable is the baby's weight gain, which is the outcome of the study.
  5. The control is the group of babies for whom the heartbeat sound was not played.

The results were consistent with the psychologist's conjecture; the babies who listened to the heartbeat sound had a greater average weight gain than the babies for whom no heartbeat sound was played.

NOW YOU CAN DO

Exercises 35–46.