Analyze Likert type items.

Description

This function will provide various statistics about a set of likert items. The resulting object will have the following items:

Usage

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likert(items, summary, grouping = NULL, factors = NULL, importance,
  nlevels = length(levels(items[, 1])))

Arguments

items

data frame containing the likert based items. The variables in the data frame should be factors.

summary

a pre-summarized data frame. The first column must be the items and the remaining columns are the levels (e.g. strongly disagree, disagree, etc).

grouping

(optional) should the results be summarized by the given grouping variable.

factors

a vector with length(factors) == ncol(items) defining which factor each column belongs to. The values correspond to the factor label.

importance

a data frame of the same dimensions as items containing an importance rating for each item. The order of columns should match and the names from items will be used.

nlevels

number of possible levels. Only necessary if there are missing levels.

Details

  • results - this data frame will contain a column 'Item', 'Group' (if a grouping variable was specified, and a column for each level of the items (e.g. agree, disagree, etc.). The value within each cell corresponds to the percentage of responses for that level and group.

  • items - a copy of the original items data frame.

  • grouping - a copy of the original grouping vector.

  • nlevels - the number of levels used in the calculations.

Value

a likert class with the following elements: results, items, grouping, nlevels, and summary.

See Also

plot.likert

summary.likert

Examples

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data(pisaitems)
items29 <- pisaitems[,substr(names(pisaitems), 1,5) == 'ST25Q']
names(items29) <- c("Magazines", "Comic books", "Fiction", 
                   "Non-fiction books", "Newspapers")
l29 <- likert(items29)
summary(l29)
plot(l29)

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