What Makes Web Sites Credible? 10 Years Later

Last month, I read a study by B. J. Fogg and others from the Persuasive Technology Lab at Stanford, entitled “What Makes Web Sites Credible? A Report on a Large Quantitative Study“. The paper described an early effort to systematically determine how different elements of web sites affect people’s perceptions of credibility (defined roughly as the intersection of trustworthiness and expertise). The original study design had 1400 participants completing a survey which presented them with 51 web site elements and asked them to rate how much more or less each element would affect the believability of a web site.

Upon reading this study, I noticed two things:

1) The original experiment solicited participants by offering to donate $10 to charity for their time; resulting in a net cost of at least $14K, raising the second question: Given the growth of sites like Mechanical Turk, can we get comparable results for less money?

2) The data was originally collected in December 2009 1999, which is almost exactly 10 years ago. Content on the web and our interactions with it have changed a great deal since then – I mean, in 1999, Google had only existed for a year, blogs were still relatively uncommon (LiveJournal had just started), and Wikipedia didn’t even exist yet! This raised the question: Given that the average Internet user now has a far greater amount of experience navigating the Web, should we expect the responses to be different 10 years later?

I decided to explore both of these questions through a survey on Mechanical Turk; in December 2009, I posted a HIT to Mechanical Turk replicating the original study as closely as possible. The 51 statements about web site elements were available from Fogg’s original paper, the same 7-point Likert scale was used, and the survey items were randomized.  I paid $0.05 per HIT, and I ended up getting 327 responses, with none thrown out due to quality.

An initial, high-level examination of the responses showed that they actually matched the 1999 data fairly well.  Average Likert ratings for each item correlated highly with average ratings for the same items in the 1999 data with R^2 = 0.96.  One difference in the data was that answers were compressed (closer to 0) overall, so for the purposes of comparison, I transformed the 2009 data using the transformation (1.1677X – 0.0003) to match the 1999 data (note that this has no effect on the correlation coefficient).

The first analysis in Fogg, et al. was to separate the various elements into 7 “scales” using factor analysis (Real-World Feel, Ease of Use, Expertise, Trustworthiness, Tailoring, Commercial Implications, and Amateurism).  Below, I present comparisons for items in each scale.  I highlighted items that deviated from the 1999 values by more than 0.25 (without the original data, I couldn’t do much more in-depth comparison), but this might give some rough idea of which elements are more important now than they were in 1999 (red) and which elements are less important (purple):

Elements related to the "Real-World" feel scale are rated similarly from 1999 to 2009.

One difference is that people seem more critical of long download times than in the past.

For some reason, it seems that displaying an award helps your site's credibility more than 10 years ago, and that providing a lot of news stories matters less.

Stating your policy on content and ending in ".org" are more important to people now - could this be a cultural shift in response to sites like Wikipedia? Overall, it seems as if links out to other sites matter less for credibility now.

Email confirmations are more important now than in 1999.

Outside advertisements and an e-commerce focus matter more for credibility now than in the past. People are paying less attention to the commercial purpose of sites, as well as the number of ads and their integration with content (Google is a favorite site for many, after all.)

People seem to notice domain name mismatches now (more public knowledge of phishing/identity theft now?), but less attention to multi-lingual sites.

People seem more willing to trust free financial sites now than in the past.

Anyways, as we might have guessed, the answers from 2009 seem to match the answers from 1999 pretty well.  The elements that made things highly credible or highly ‘un-credible’ in the past seem to have remained constant, and those which didn’t matter then seem not to matter too much now.  Some interesting elements are noted in the captions with some rough conjectures as to why some of them might be trending the way they are.

The rest of the Fogg paper focused on characterizing differences in scale responses due to demographic differences between participants, but I found that part of the study less convincing as they averaged over the positively and negatively phrased elements on each scale (which I think makes the interpretation somewhat confusing).

Now, back to our two questions:

1) It looks as if using Mechanical Turk, we were able to get reasonable answers that fairly closely matched those from the original study.  Total price tag: 327 response * $0.05 = $16.35 paid to participants (plus Amazon’s cut), which made this study about $13,980 cheaper than the original one.

2) We see above a few small changes in what makes web sites credible, but overall, people are looking at the same things, meaning that we should continue taking the same factors into account when designing websites. I’ve made some guesses as to why these elements may have changed over time, but I’m curious to hear what you think, so leave a comment!