As an exercise on programming Android, I've made an app to log predictions you make and keep score of your results. Like PredictionBook, but taking more of a personal daily exercise feel, in line with this post.

The "statistics" right now are only a score I copied from the old Credence calibration game, and a calibration bar chart.

I'm hoping for suggestionss for features and criticism on the app design.

Here's the link for the apk (v0.4), and here's the source code repository. You can download it at Google Play Store.

Pending/Possible/Requested Features:

  • Set check-in dates for predictions
  • Tags (and stats by tag)
  • Stats by timeframe
  • Beeminder integration
  • Trivia questions you can answer if you don't have any personal prediction to make
  • Ring pie chart to choose probability


2015-08-26 - Fixed bug that broke on Android 5.0.2 (thanks Bobertron)

2015-08-28 - Change layout for landscape mode, and add a better icon

2015-08-31 -

  • Daily notifications
  • Buttons at the expanded-item-layout (ht dutchie)
  • Show points won/lost in the snackbar when a prediction is answered
  • Translation to portuguese


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Thanks, this is awesome. I would love if there was a "roulette wheel" widget to choose the probability, in order to better visualize the equivalent bet test.

I'm not sure I get what kind of roulette you mean... something like a ring pie chart?

I thought of using a target, but I'm not sure if that would be much more effective than the sliding bar.


Yes, the ring pie chart.


Really fantastic idea. I would suggest adding a way to tag predictions so that you can see how accurate you are within a particular domain. I would also suggest adding a way to see your accuracy over different timeframes (in order to view improvement). With those two features, this would definitely be an app I'd be willing to buy.

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Thanks! I'll look into adding tags and timeframes. I'm not sure how to do that without the layout getting too crowded.

Sounds nice. Making predictions about personal events makes more sense to me than predicting e.g. elections or sport events (beauce a) I don't know anything about it, and b) I don't care about it). But I don't like the idea of making them (all) public, like on prediction book. Though a PredictionBook integration sounds like an obvious fancy feature.

And I liked what I saw the one second I could use the app ;-)

After installing, it crashed pressing "save" on the first prediction. Now it chrashed right on startup. I get to see the app for a moment, but I can't do anything. After deleting the data (from the android setting) I can make a new prediction, but again, it crashes after pressing "save".

I installed from the apk-link you provided.

I've got a Moto G (2. Generation) with Android 5.0.2.

Hope that helps. And if anyone can tell me how to diagnose the problem in more detail, I'd be interested in that, too.

Check the link below, v0.2. Should be working now!

Great! Works so far.

This is weird. I'll test to see if I can reproduce and report back (hopefully with a fix).

I like it! Thoughts from 30 seconds of playing around:

  • There's some flickering in the text of the tabs while swiping between them.
  • What is the difference between a "Yes" and a "No" prediction?
  • Long presses are not particularly discoverable; perhaps there should be some buttons when you tap a prediction to expand it in the list view.

Design-wise, it's great apart from that. Both of your proposed features would be worthwhile too.


  • I'm not getting the flickering here... are you on a low-end device? Which version of android are you on?
  • No difference at all. I just thought it would make sense to phrase the predictions in the form of questions and answers - so you could e.g. pick a question from a pre-made list and just choose your answer.
  • Good to know, I thought "long press to edit" was a common enough pattern that everybody would discover it.

It's a Moto X (2nd gen) with Android 5.1, so not particularly low-end. It is most obvious if I slide only just fast enough for the inertia to take it between tabs, then it appears to get confused as to which one is highlighted at the crossover point.