Landline phone numbers in electronic forms

In September 2009, we published data showing typical ways that users enter their mobile/cell number into an electronic form. This data was a by-product of some research that Jessica Enders, Principal of Formulate, conducted for SEEK.

To refresh your memory, we show again, in Figure 1, the invitation that was used to recruit a random selection of users from the SEEK website, for the research project.

Figure 1: Invitation used to recruit research participants.

Users were free to enter whichever phone number they wanted into the box titled “Your Phone Number”, and there was no validation.

Given this design, we can use the phone number data to get a sense of how the majority of Australians provide their phone number, by default. In this post, we're going to look at landline phone numbers. Thanks go again to the team at SEEK for allowing access to this invaluable data.

About Australian landline phone numbers

In Australia, landline phone numbers have 8 digits, plus a 2 digit area code that always starts with a 0. For example: (02) 9876 1234.

The area code indicates which geographic region the number comes from. For instance, an area code of “03” covers the south east, including the states of Victoria and Tasmania, and some of the bottom of New South Wales. There are only four area codes in total: “02”, “03”, “07” and “08”.

Because in Australia there are only four area codes covering a total of only eight states and territories, people frequently know the area code for places other than where they live. This means that when it comes to landlines, often one only has to remember an 8 digit number (rather than the 10 digits of a mobile).

Still, 8 digits is a reasonably long string, so some people break the number up, as we did in the example above. Here the number is broken into two lots of 4 digits, separated by a space. (The 2 digits of the area code, in the example above, are given in parentheses and separated from the number by a space.)

Based on our anecdotal experience, we were fairly confident that this would be a standard approach to chunking landline numbers. If there was a consistent pattern, this could suggest an ideal default method for collecting such numbers. However, we saw the need to test this hypothesis, and the SEEK data provided a great opportunity.

The research findings: one long string is the clear winner

Like the mobile phone numbers, one long string of digits — including area code — was the most common method of data entry: out of 640 landline phone numbers provided by interested research participants, 39% were entered as one long string of 10 digits (i.e. no spaces and no chunking). This gives weight to the argument proposed by Russ Weakley that users have learnt to be wary of breaking up numbers, in such form fields, lest they trigger a validation failure.

Another 35% of landline numbers had the 2 digits for the area code separated from the main number by a space:

  • for 18% of landline numbers, the remaining 8 digits were provided as an unbroken string (e.g. 07 12345678)
  • for 17% of landine numbers, the remaining 8 digits were chunked into two sets of 4 digits (e.g. 07 1234 5678).

Interestingly, in another 11% of cases, the 8 digits of the main part of the landline number were given, unbroken, but also without the area code, despite it being explicitly requested via a caption next to the field. If we had had validation on the field, this means that over 10% of users would have experienced a validation failure.

Another long tail

A further 10 different ways of entering the landline phone number each occurred 1% or 2% of the time, making up 12% of the sample in total. These included the format we expected to be most popular — 2 digit area code in parentheses, a space, 4 digits, a space, 4 digits, e.g. (02) 9876 1234 — which only represented 2% of the total sample. (Just goes to show how important it is to test your hypotheses!)

This long tail also included another 2% of numbers that omitted the area code, but had the main number chunked into two groups of 4 (e.g. 5678 1234).

In total there were 32 variants on the way people entered their landline phone number into the text field. This compares to 44 variants for mobile phone numbers. As with mobiles, there was a considerable amount of diversity in the variants, including:

  • Different chunking to suit the particular digits in the number,
    e.g. 03 971 97974.
  • Different chunking unrelated to the particular digits in the number,
    e.g. 021234 5678.
  • Different ways to include the country code,
    e.g. +61712341234, and 61-7-1234-1234.

What does it all mean?

To allow for the diversity of use a landline text field should accept at least 12 characters (10 digits plus 2 spaces) but is best kept as a single text field, rather than being chunked. The form should also:

  • give an example of formats that will be accepted; and
  • make it clear whether country code is needed.

But wait, there's more!

In early 2010 we will publish the third and final post on this particular piece of research. The post will examine the:

  • proportional preference, when being asked to provide a phone number, for mobiles compared to landlines; and
  • overall error rates for the provision of phone numbers.

Should be interesting stuff for e-commerce and web form managers everywhere, as it will provide insight into the need for validation, as well as users’ preferences.