Multiple linear regression coefficients (B) for diastolic blood pressure (DBP) on genetic ancestry, ascribed <i>color</i>, socioeconomic status, α_2C adrenergic receptor genotype, and standard covariates.

<p>Body mass index (BMI  =  weight kg/(height m)²); SES  =  socioeconomic status; antihypertensive  =  self-reported use of antihypertensive medication.</p

Multiple linear regression coefficients (b) for systolic blood pressure (SBP) on genetic ancestry, ascribed <i>color</i>, socioeconomic status, α_2C adrenergic receptor genotype, and standard covariates.

<p>Body mass index (BMI)  =  weight kg/(height m)²; SES  =  socioeconomic status; antihypertensive  =  self-reported use of antihypertensive medication.</p

Descriptive statistics for study variables.

<p>Means (SD) are reported for continuous variables, percentages for categorical variables.</p>*<p>ANOVA shows statistically significant differences across categories of <i>color</i> for education and African ancestry.</p

Interaction effect between culturally ascribed <i>color</i> and socioeconomic status for (A) systolic blood pressure and (B) diastolic blood pressure, adjusted for age, sex, body mass, use of antihypertensive medications, and genetic ancestry.

<p>Interaction effect between culturally ascribed <i>color</i> and socioeconomic status for (A) systolic blood pressure and (B) diastolic blood pressure, adjusted for age, sex, body mass, use of antihypertensive medications, and genetic ancestry.</p

Open-ended interview questions and saturation

<div><p>Sample size determination for open-ended questions or qualitative interviews relies primarily on custom and finding the point where little new information is obtained (thematic saturation). Here, we propose and test a refined definition of saturation as obtaining <i>the most salient items</i> in a set of qualitative interviews (where items can be material things or concepts, depending on the topic of study) rather than attempting to obtain <i>all the items</i>. Salient items have higher prevalence and are more culturally important. To do this, we explore saturation, salience, sample size, and domain size in 28 sets of interviews in which respondents were asked to list all the things they could think of in one of 18 topical domains. The domains—like kinds of fruits (highly bounded) and things that mothers do (unbounded)—varied greatly in size. The datasets comprise 20–99 interviews each (1,147 total interviews). When saturation was defined as the point where less than one new item per person would be expected, the median sample size for reaching saturation was 75 (range = 15–194). Thematic saturation was, as expected, related to domain size. It was also related to the amount of information contributed by each respondent but, unexpectedly, was reached more quickly when respondents contributed <i>less</i> information. In contrast, a greater amount of information per person increased the retrieval of <i>salient</i> items. Even small samples (<i>n</i> = 10) produced 95% of the most salient ideas with exhaustive listing, but only 53% of those items were captured with limited responses per person (three). For most domains, item salience appeared to be a more useful concept for thinking about sample size adequacy than finding the point of thematic saturation. Thus, we advance the concept <i>of saturation in salience</i> and emphasize probing to increase the amount of information collected per respondent to increase sample efficiency.</p></div

Estimated point of saturation and domain size.

<p>Estimated point of saturation and domain size.</p

The examples.

<p>The examples.</p

The number of unique items provided with increasing sample size when there are three or fewer responses per person.

<p>The number of unique items provided with increasing sample size when there are three or fewer responses per person.</p

Capture of salient items with full free list and with three or fewer responses.

<p>Capture of salient items with full free list and with three or fewer responses.</p

Comparison of number of unique items obtained with full free lists and with three or fewer responses.

<p>Comparison of number of unique items obtained with full free lists and with three or fewer responses.</p