The BMI z-score is a relative measure of body mass index (BMI) that takes into account age. Higher values represent heavier individuals for a given height. The table here shows the BMI z-score of pre- and post-pubertal girls at three ages.

Which of the following conclusions can you draw from the data?
a. At a given age, there are more girls with low BMI z-scores than with high BMI z-scores.
b. At a given age, girls with high BMI z-scores are more likely to have begun puberty than girls with low BMI z-scores.
c. Girls 11, 12, and 13 years of age are equally likely to have begun puberty.
d. There is no relationship between BMI z-score and age of beginning puberty.

Verified step by step guidance

1. Examine the table to understand the relationship between age, BMI z-score, and pubertal status. Note that the table provides BMI z-scores for pre-pubertal and post-pubertal girls at ages 11, 12, and 13.
2. Observe that for each age group, the BMI z-score is higher for post-pubertal girls compared to pre-pubertal girls. This suggests a trend where girls with higher BMI z-scores are more likely to have begun puberty.
3. Consider option a: 'At a given age, there are more girls with low BMI z-scores than with high BMI z-scores.' The table does not provide information on the number of girls, only the average z-scores, so this conclusion cannot be drawn.
4. Consider option b: 'At a given age, girls with high BMI z-scores are more likely to have begun puberty than girls with low BMI z-scores.' The data supports this conclusion as post-pubertal girls have higher BMI z-scores at each age.
5. Consider options c and d: 'Girls 11, 12, and 13 years of age are equally likely to have begun puberty' and 'There is no relationship between BMI z-score and age of beginning puberty.' The data shows a decrease in BMI z-score with age for post-pubertal girls, suggesting a relationship between BMI z-score and pubertal status, thus these options are not supported.

Key Concepts

BMI z-score

The BMI z-score is a statistical measure that indicates how a person's body mass index (BMI) compares to a reference population, adjusted for age and sex. A z-score of 0 represents the average BMI for a specific age group, while positive values indicate above-average BMI and negative values indicate below-average BMI. This measure is particularly useful in assessing growth patterns in children and adolescents.

Puberty and its effects on BMI

Puberty is a developmental stage characterized by physical and hormonal changes that lead to sexual maturity. During this period, individuals often experience significant changes in body composition, including increases in muscle mass and fat distribution, which can affect BMI. Understanding the timing of puberty is crucial for interpreting BMI z-scores, as those who have begun puberty may show higher BMI z-scores compared to their pre-pubertal peers.

Interpreting data from tables

Interpreting data from tables involves analyzing numerical values to draw conclusions about trends or relationships. In this case, the table presents BMI z-scores for pre- and post-pubertal girls at different ages, allowing for comparisons between groups. Recognizing patterns, such as the increase in post-pubertal BMI z-scores and the decrease in pre-pubertal scores with age, is essential for answering questions about the relationship between BMI and puberty.