All content on this site is by and copyright ©1994-2023 Tonio Loewald, unless otherwise specified. Best viewed in Firefox, Safari, or IE8.

Frequently Asked Questions

A program for designing, creating, deploying, and managing Questionnaire-based studies on Windows, Macs, and online.

Frequently Asked Questions

How accurate are the timers used in RiddleMeThis?

The short version is "pretty accurate" — typical user response times (actual paper behind paywall) are 0.2s for keystrokes, 1.1s for mouse pointing, 0.4s to move hand between keyboard and mouse, and 1.3s to mentally prepare for an action. Barring some kind of computer "hiccup", the expected timing uncertainties are very small (e.g. 1/60th of a second for screen refresh, 1ms for OS level timer).

The long version goes like this: RiddleMeThis attempts to minimize the most obvious source of timing inaccuracy (file loading latency) by preloading assets before attempting to display a screen and starting a timer. The same technique also eliminates a major potential source of timing inaccuracies between web browsers, some of which will draw a partially loaded screen while others will not.

It is unclear what the delay between a program telling the OS to draw an image on the screen and its appearing on a user's monitor might be, it may vary anywhere between 0 and 3 screen refresh cycles (where the higher value is likely to coincide with quicker refresh cycles). A "worst case scenario" would probably be on the order of 1/30th of a second.

In practice there are many other potential sources of innaccuracy, especially for web-based questionnaires. Anyone who has used a web browser will have experienced odd delays, even when using a very new, fast computer. The fact that users will typically be using their computers for many things at once further complicates things: what happens if, say, a new MP3 loads in the middle of one interaction, or a Flash video in another browser tab causes a performance hiccup?

Then there are different response times for different input devices and their drivers, OS-level deficiencies (e.g. see here), system performance, and even browser performance (even if the OS-level timer is accurate to within 1ms, the execution time of the code may vary greatly, e.g. the performance of JavaScript in different browsers on the same computer varies by a factor of 20 today.).

It would therefore be foolhardy to claim accuracy any better than twice a typical screen refresh period, or 1/30th of a second. Any questionnaire conducted over the web is clearly going to have more unknowns that one conducted in a lab; it seems unlikely that these technical issues will be a significant component of this.

How big can my questionnaire get?

Big. Some OS-dependent limits may exist (e.g. under OS X a listbox can only have so many thousand rows). It's probably best not to put too many questions in a section. Let us know if you need more questions in your questionnaire than RiddleMeThis can cope with...

If I want to create forms on a Mac and deploy them on Windows (or vice-versa) do I need to register twice?

No, you don't. Just register the version on the computer you'll be creating forms with.

OK, what if I want to use it on two or more computers?

Register each copy. Or talk to us about volume/site licenses.

Can I give away the RiddleMeThis Runtime? Distribute it on CDs? Is there a royalty?

Yes. Sure thing. No. We do, however, retain copyright, and you may not remove our copyright notices.

The unregistered version of RiddleMeThis only exports the first five rows of data gathered with a questionnaire. Are the extra rows of data lost?

Yep they're gone... Just kidding. They're there. You can retrieve them manually, or register RiddleMeThis and export them automatically.

I'm using RiddleMeThis (on a Windows PC) and I can't seem to import images or videos into my questionnaire. Is this a bug?

Currently, RiddleMeThis requires QuickTime to be installed in order to support images and video. QuickTime is free from Apple.

We plan to make RiddleMeThis less dependent on QuickTime in future (we can't really avoid using it for video, but we can avoid using it for images).


What are your consulting rates?

We're very good value for money!

How much do you charge for custom features?

We don't want to support multiple versions of RiddleMeThis, so any new custom feature will either be implemented via external programs or become a fully functional new feature of RiddleMeThis. In the latter case, if you're willing to wait for us to get around to it, the cost is zero.

If you must have your feature now, we'll charge our usual consulting rates (possibly discounted if we would have added the feature eventually).

Online Features

Which web browsers can view RiddleMeThis forms online?

If you don't use video in forms, any graphical browser will work.

If you don't use pictures, even text-based browsers (e.g. Lynx) will work.

Which web servers support PHP?

Just about any you're likely to want to use. Visit for more information.

Do you host questionnaires on your web servers?

Not yet, but soon perhaps! We're looking at demand and pricing. We want to keep it as cheap and simple as possible.

Why PHP?

It's the most popular plugin for the world's most popular web server (Apache). It's free. It comes pre-installed on Mac OS X 10.2. It's very stable. It's slightly easier (for our purposes) than Perl. Did I mention it's free?

Do you use any special PHP plugins or databases?

The current online RiddleMeThis implementation stores data as text files. While this has the advantage of requiring no significant configuration and being very robust, it has security issues especially for users who are sharing space on virtual servers, etc.

We plan to give users the option of storing their data in any one of a number of (free) databases or hosting their forms on our (secure and reliable) servers for a relatively low charge.

What platforms support PHP?

Windows. Mac OS X. Pretty much all flavors of Linux and UNIX. Most web hosting services.

How do I set PHP up on my computer?

Windows 98/ME/NT/2000/XP: the easiest way to run PHP under Windows is EasyPHP, which you can get here.

Mac OS X: The easiest way to run PHP on your Mac is MAMP, which you can get here.

Linux/UNIX: it's almost certainly installed already. In the unlikely event that you don't have PHP pre-installed, you can probably get it easily or compile your own. (E.g. if you need to collect data in the field by hand, you can ... or so we've been led to believe ... easily install Apache + PHP on a Sharp Zaurus PDA and run RiddleMeThis questionnaires on it.)

BeOS: yep, there's a version of PHP for BeOS. Click here.

Other Platforms: has links to binaries for AmigaOS, Novell Netware, OS/2, SGI Irix, and other operating systems. About the only platforms that can't serve PHP are Palm OS and PocketPC. Of course you can still use Palm and PocketPC web browsers to fill in a questionnaire...

If I create my own form.rmt file, can I use your PHP runtime?

Important Change! We've decided to release the online runtime under the LGPL. See below.

Yes. Our php runtime is licensed under the GNU Lesser General Public License. There's nothing to stop you making your own commercial form.rmt editor and selling it along with our runtime. (However, it's not a total freebie, please read the license.)

If for some reason you prefer to create form.rmt files using programs of your own devising, please... tell us what we're doing wrong!

Can I modify the PHP runtime to suit my own purposes?

Absolutely -- subject to the provisions of the LGPL. See above.

Other Topics

Can RiddleMeThis provide answer keys? Can I use RiddleMeThis to run exams in a classroom (or virtual classroom)?

Yes and no. RiddleMeThis is focussed on doing questionnaire-based studies at the moment. We don't want to get too distracted adding features not related to this right now. Eventually, we plan to provide very powerful support for creating online teaching solutions (e.g. provide for feedback rather than simply scoring results).

That said, it's very easy to use RiddleMeThis for running exams -- all you need to do is set up your exam as a questionnaire (make sure there's a question for identifying the student!). To create an answer key, simply do the questionnaire yourself and answer the questions correctly. Then export the data to Excel and use a simple comparison formula to grade your exams.

Hey, isn't that a Jester in your icons?

Well, as you may figure out by visiting we might run into some trademark issues if we used a "riddler"