# jspsych-survey-likert plugin

The survey-likert plugin displays a set of questions with Likert scale responses. The subject responds by selecting a radio button.

## Parameters

This table lists the parameters associated with this plugin. Parameters with a default value of *undefined* must be specified. Other parameters can be left unspecified if the default value is acceptable.

Parameter | Type | Default Value | Description
----------|------|---------------|------------
questions | array | *undefined* | Each array element is an array of strings. The strings are the prompts/questions that will be associated with a slider. All questions within an array will get presented on the same page (trial). The length of the questions array determines the number of trials.
labels | array |  *undefined* | Each array element is an array of arrays. The innermost arrays contain a set of labels to display for an individual question. The length of this array will determine the number of response options for that question. If you want to use blank responses and only label the end points or some subset of the options, just insert a blank string for the unlabelled responses. The middle level of arrays groups together the sets of labels that appear in a single trial. This level should correspond to the `questions` array.

## Data Generated

In addition to the [default data collected by all plugins](overview#datacollectedbyplugins), this plugin collects the following data for each trial.

Name | Type | Value
-----|------|------
responses | JSON string | A string in JSON format containing the responses for each question. The encoded object will have a separate variable for the response to each question, with the first question in the trial being recorded in `Q0`, the second in `Q1`, and so on. The responses are recorded as integers, representing the position of the slider on the scale.
rt | numeric | The response time in milliseconds for the subject to make a response. The time is measured from when the questions first appear on the screen until the subject's response.

## Examples

#### Basic example with multiple questions on a page.

```javascript
// defining groups of questions that will go together.
var page_1_questions = ["I like vegetables.", "I hate eggs."];
var page_2_questions = ["I like fruit."];

// defining two different response scales that can be used.
var scale_1 = ["Strongly Disagree", "Disagree", "Neutral", "Agree", "Strongly Agree"];
var scale_2 = ["Strongly Disagree", "", "", "Neutral", "", "", "Strongly Agree"];

var likert_block = {
    type: 'survey-likert',
    questions: [page_1_questions, page_2_questions],
    labels: [[scale_1, scale_2], [scale_1]], // need one scale for every question on a page
};
```