emmeans (version 1.8.8)

auto.noise: Auto Pollution Filter Noise

Description

Three-factor experiment comparing pollution-filter noise for two filters, three sizes of cars, and two sides of the car.

Usage

auto.noise

Format

A data frame with 36 observations on the following 4 variables.

noise

Noise level in decibels (but see note) - a numeric vector.

size

The size of the vehicle - an ordered factor with levels S, M, L.

type

Type of anti-pollution filter - a factor with levels Std and Octel

side

The side of the car where measurement was taken -- a factor with levels L and R.

Details

The data are from a statement by Texaco, Inc., to the Air and Water Pollution Subcommittee of the Senate Public Works Committee on June 26, 1973. Mr. John McKinley, President of Texaco, cited an automobile filter developed by Associated Octel Company as effective in reducing pollution. However, questions had been raised about the effects of filters on vehicle performance, fuel consumption, exhaust gas back pressure, and silencing. On the last question, he referred to the data included here as evidence that the silencing properties of the Octel filter were at least equal to those of standard silencers.

Examples

# (Based on belief that noise/10 is in decibel units)
noise.lm <- lm(noise/10 ~ size * type * side, data = auto.noise)

# Interaction plot of predictions
emmip(noise.lm, type ~ size | side)

# Confidence intervals
plot(emmeans(noise.lm, ~ size | side*type))