In-survey calculations: how to calculate a wait time and adapt the questionnaire text based on the answer

You perform in-survey calculations in Snap using derived variables.

You can display the content of the derived variable in the questionnaire and/or show or hide other parts of the questionnaire depending on their value.

Derived variables are created from responses to other variables. The way you create them will be different for each type of derived variable.

For example, you could display a derived value in the questionnaire to:

• add up costs to display a total (in a derived quantity variable)
• add a title to someone’s name (in a derived literal variable).

If you want to change the content shown in the questionnaire, you can choose what to show by testing the value of a derived variable. You can:

• change text depending on the result
• show or hide questions and text depending on the result
• use routing to jump to different parts of the questionnaire depending on the result.

This example assumes that the appointment time is stored in Q1 and the time the respondent was seen (if later) is stored in Q2.

1. Click  to display the Variables Window.
2. Click to add a new variable.
3. Specify the Variable details:
   Name: Delay.
   Label: Wait time to see pharmacist.
   Type: Derived (the variable will derive its data from the other time variables).
   Response: Quantity (the variable will hold a number of seconds).
   
4. Set the value for the Valid code to be Q2-Q1 to get the difference between the times. (Note that this calculation assumes that Q2 is greater than Q1.)
5. Click to save the variable.

Times in Snap are stored in seconds. The derived variable calculates time ranges in seconds and bands the result.

1. Click  on the Snap toolbar to display the Variables window.
2. Click  on the Variables window toolbar to add a new variable.
3. Specify the Variable details:
   Name: delayband.
   Label: Delay codes used for apology.
   Type: Derived (the variable will derive its data from the Delay variable that you have just created).
   Response: Single (the data will be coded into bands).
4. Double click in the first code label and enter appt time ok. This is a delay of less than ten minutes.
   
5. Press [Tab] to move to the Values column. Enter delay < 601. This is a delay of ten minutes or less.
6. Press [Tab] to move to the next code label field and enter more than ten minutes. Then enter delay < 1200 as the Value. This is the range ten to twenty minutes. Since the codes are checked in order, a value less than ten minutes will already have been coded.
7. Press [Tab] to move to the next code label and enter more than twenty minutes. Then enter delay < 3600 as the Value. This is the range twenty to sixty minutes.
8. Press [Tab] to move to the next code label and enter more than an hour. Then enter true as the Value. This catches all numbers above 3600 seconds.
9. Click  to save the derived variable.

The text in the code labels 2, 3 and 4 will be text substituted (piped) into the questionnaire when appropriate. It will not be necessary to show the text in code label 1 in the questionnaire.

1. Click to change to the Questionnaire view.
2. Go to the end of the questionnaire and press enter to create a new variable.
3. Change the type to Instruction and type in first message text “That’s great, we aim to see all visitors within 10 minutes of their allotted appointment time.”
4. Press enter to create another instruction.
5. Insert the first part of the apology “We are very sorry to hear that you had to wait”
6. Check the toolbar topic is set to Font, click the [Insert…] button on the Questionnaire window toolbar and select Variable Field from the menu.
7. The New variable field dialog appears. Select delayband as the variable and Reply as the aspect.
   
8. Click [OK]. Snap will display the question name within curly brackets {delayband}, to show that it is a text-substituted field.
9. Add the text “Please accept out apologies.”
10. Click  to save your changes.

1. Select your instruction for no delay and click  on the Questionnaire window toolbar to open the Routing Rules dialog.
2. Click [Add] to create a new rule and set the type to Conditionally Ask Question. Click [OK].
3. Enter delayband = 1 in the If field and click [OK]. This instruction will be shown if they had to wait less than ten minutes.
   
4. Select the instruction for the apology and add a new routing rule in the same way as in step 3 but this time set the If field to delayband > 1 and click [OK]. This instruction will be shown if they had to wait longer than ten minutes.

1. Publish the survey with Preview enabled.
2. Click through the preview, entering different appointment times and times you were seen. Confirm that the apology appears with the correct text if the delay is between ten and twenty minutes, over twenty minutes or over an hour. Confirm that the appreciation appears if the delay is ten minutes or less.