Actigraphs have been used to assess children's activity patterns and quality of sleep. Which of the following is not true based on findings from studies using these devices?
1) Actigraphs provide accurate measurements of children's activity levels.
2) Actigraphs can be used to monitor sleep duration and efficiency.
3) Actigraphs have been found to be ineffective in assessing sleep quality.
4) Actigraphs are a useful tool for studying children's sleep patterns.
