In order to study drug use and it's effects on newborn baby weights, babies that were born in three randomly selected states in the US were used in a national study. Two thousand, three hundred and twenty-three babies that were born in those states in 2025 were then randomly selected to be part of the study. Information on each baby was recorded. What is the sample?

Sex (male/female)
Weight (in grams)
Gestation (full term birth/ premature birth)
Did the mother use illicit drugs during pregnancy? (yes/no)
Did the mother smoke cigarettes during pregnancy? (yes/no)
Did the mother have gestational diabetes during pregnancy? (yes/no)

Question

In order to study drug use and it's effects on newborn baby weights, babies that were born in three randomly selected states in the US were used in a national study. Two thousand, three hundred and twenty-three babies that were born in those states in 2025 were then randomly selected to be part of the study. Information on each baby was recorded. What is the sample?

Sex (male/female)
Weight (in grams)
Gestation (full term birth/ premature birth)
Did the mother use illicit drugs during pregnancy? (yes/no)
Did the mother smoke cigarettes during pregnancy? (yes/no)
Did the mother have gestational diabetes during pregnancy? (yes/no)

BlackTom AI · Accepted Answer

A sample is the subset of individuals actually observed and measured from a larger population. Key concepts: population vs. sample, sampling frame, and multistage/random sampling. Here the researchers first selected three states at random and then randomly selected individual babies born in those states in 2025. That two-step design is a form of multistage sampling; the measured variables (sex, weight, gestation, drug use, smoking, gestational diabetes) are recorded for each selected baby.

Step-by-step reasoning:
1. Identify the population of interest: likely all newborn babies relevant to the study (e.g., newborns in the US or newborns born in 2025). The problem description focuses on babies born in three randomly selected states, but those are the sampling units from which observations are drawn, not the entire population.
2. Identify what was actually observed: "Two thousand, three hundred and twenty-three babies that were born in those states in 2025 were then randomly selected to be part of the study. Information on each baby was recorded."
3. Therefore the sample consists of those 2,323 babies — they are the individuals on which measurements were taken.

No numerical calculation beyond noting the sample size: sample size n = 2323.

Why this is correct: the sample is defined as the set of subjects actually selected and measured. The phrase explicitly states 2,323 babies were randomly selected and information recorded on each, which by definition is the sample.

Why other possible answers would be incorrect:
- The three states are not the sample; they are the first-stage clusters or strata used to draw the sample.
- All babies born in those states (the full populations of those states) were not observed; only a random subset of 2,323 were.
- The variables listed are measurements collected on the sample, not the sample itself.

Conclusion: The correct sample is the 2,323 babies born in 2025 that were selected, matching the provided answer.

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