xmpl {prefmod}

Data (Likert items): Example Data Set

Description

Data to illustrate the usage of patt.design for rating scale (Likert type) items.

Usage

xmpl

Format

A data frame with 100 observations on 5 numeric variables. The first three variables (I1, I2, I3) are the rating scale (Likert type) items with 5 response categories, ranging from 1 (strong agreement) to 5 (strong disagreement).

I1

response to item 1

I2

response to item 2

I3

response to item 3

SEX

(1) male, (2) female

EDU

(1) low education, (2) high education

Details

Datasets in data files or Data frames used in patt.design require the following structure:

• All values must be numeric.

• The item responses must be in the leftmost columns (such as I1 to I3 above).

• Categorical subject covariates follow the item responses (rightmost columns) and their levels must be specified as consecutive integers. If in a used datafile or dataframe these are defined as R factors they will be converted to integers. This is not possible if characters are used as factor levels and, consequently, patt.design will produce an error.

Examples

des <- patt.design(xmpl, nitems = 3, resptype = "rating", cov.sel = "SEX")
head(des)