# survey-likert

Current version: 2.0.0. [See version history](https://github.com/jspsych/jsPsych/blob/main/packages/plugin-survey-likert/CHANGELOG.md).

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

## Parameters

In addition to the [parameters available in all plugins](../overview/plugins.md#parameters-available-in-all-plugins), this plugin accepts the following parameters. 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* | An array of objects, each object represents a question that appears on the screen. Each object contains a prompt, labels and required parameter that will be applied to the question. See examples below for further clarification.`prompt`: Type string, default value is *undefined*. The strings are the question that will be associated with a slider. `labels`: Type array, default value is *undefined*. Each array element is an array of strings. The innermost arrays contain a set of labels to display for an individual 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 unlabeled responses.`required`: Type boolean, default value is false. Makes answering questions required. `name`: Name of the question. Used for storing data. If left undefined then default names (`Q0`, `Q1`, `...`) will be used for the questions.
randomize_question_order | boolean | `false` | If true, the display order of `questions` is randomly determined at the start of the trial. In the data object, `Q0` will still refer to the first question in the array, regardless of where it was presented visually.
preamble | string | empty string | HTML formatted string to display at the top of the page above all the questions.
scale_width | numeric | null | The width of the likert scale in pixels. If left `null`, then the width of the scale will be equal to the width of the widest content on the page.
button_label | string |  'Continue' | Label of the button.
autocomplete | boolean | false | This determines whether or not all of the input elements on the page should allow autocomplete. Setting this to true will enable autocomplete or auto-fill for the form.

## Data Generated

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

Name | Type | Value
-----|------|------
response | object | An object containing the response for each question. The object will have a separate key (variable) for 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 selected on the likert scale for that question. If the `name` parameter is defined for the question, then the response object will use the value of `name` as the key for each question. This will be encoded as a JSON string when data is saved using the `.json()` or `.csv()` functions. |
rt | numeric | The response time in milliseconds for the participant to make a response. The time is measured from when the questions first appear on the screen until the participant's response(s) are submitted. |
question_order | array | An array with the order of questions. For example `[2,0,1]` would indicate that the first question was `trial.questions[2]` (the third item in the `questions` parameter), the second question was `trial.questions[0]`, and the final question was `trial.questions[1]`. This will be encoded as a JSON string when data is saved using the `.json()` or `.csv()` functions. |

## Install

Using the CDN-hosted JavaScript file:

```js
<script src="https://unpkg.com/@jspsych/plugin-survey-likert@2.1.0"></script>
```

Using the JavaScript file downloaded from a GitHub release dist archive:

```js
<script src="jspsych/plugin-survey-likert.js"></script>
```

Using NPM:

```
npm install @jspsych/plugin-survey-likert
```
```js
import surveyLikert from '@jspsych/plugin-survey-likert';
```

## Examples

???+ example "Single Question"
    === "Code"

        ```javascript
        var trial = {
          type: jsPsychSurveyLikert,
          questions: [
            {
              prompt: "I like vegetables.", 
              labels: [
                "Strongly Disagree", 
                "Disagree", 
                "Neutral", 
                "Agree", 
                "Strongly Agree"
              ]
            }
          ]
        };
        ```

    === "Demo"
        <div style="text-align:center;">
          <iframe src="../../demos/jspsych-survey-likert-demo1.html" width="90%;" height="500px;" frameBorder="0"></iframe>
        </div>

    <a target="_blank" rel="noopener noreferrer" href="../../demos/jspsych-survey-likert-demo1.html">Open demo in new tab</a>

???+ example "Multiple questions in a random order"
    === "Code"

        ```javascript
        var likert_scale = [
          "Strongly Disagree", 
          "Disagree", 
          "Neutral", 
          "Agree", 
          "Strongly Agree"
        ];

        var trial = {
          type: jsPsychSurveyLikert,
          questions: [
            {prompt: "I like vegetables.", name: 'Vegetables', labels: likert_scale},
            {prompt: "I like fruit.", name: 'Fruit', labels: likert_scale},
            {prompt: "I like meat.", name: 'Meat', labels: likert_scale},
          ],
          randomize_question_order: true
        };
        ```

    === "Demo"
        <div style="text-align:center;">
          <iframe src="../../demos/jspsych-survey-likert-demo2.html" width="90%;" height="500px;" frameBorder="0"></iframe>
        </div>

    <a target="_blank" rel="noopener noreferrer" href="../../demos/jspsych-survey-likert-demo2.html">Open demo in new tab</a>