nutrition: Nutrition data

In emmeans: Estimated Marginal Means, aka Least-Squares Means

Nutrition data

Description

This observational dataset involves three factors, but where several factor combinations are missing. It is used as a case study in Milliken and Johnson, Chapter 17, p.202. (You may also find it in the second edition, p.278.)

Usage

nutrition

Format

A data frame with 107 observations and 4 variables:

age

a factor with levels 1, 2, 3, 4. Mother's age group.

group

a factor with levels FoodStamps, NoAid. Whether or not the family receives food stamp assistance.

race

a factor with levels Black, Hispanic, White. Mother's race.

gain

a numeric vector (the response variable). Gain score (posttest minus pretest) on knowledge of nutrition.

Details

A survey was conducted by home economists “to study how much lower-socioeconomic-level mothers knew about nutrition and to judge the effect of a training program designed to increase their knowledge of nutrition.” This is a messy dataset with several empty cells.

Source

Milliken, G. A. and Johnson, D. E. (1984) Analysis of Messy Data – Volume I: Designed Experiments. Van Nostrand, ISBN 0-534-02713-7.

Examples

nutr.aov <- aov(gain ~ (group + age + race)^2, data = nutrition)

# Summarize predictions for age group 3
nutr.emm <- emmeans(nutr.aov, ~ race * group, at = list(age="3"))
                   
emmip(nutr.emm, race ~ group)

# Hispanics seem exceptional; but this doesn't test out due to very sparse data
pairs(nutr.emm, by = "group")
pairs(nutr.emm, by = "race")

emmeans documentation built on Oct. 14, 2024, 5:07 p.m.