As the level number increases, the number of actual causes grow from one to two, there may be a delay between exposure and evidence of symptom, and it may not be certain that a person exposed ever gets symptoms. You can tell how many actual causes, the delay, and the probability of showing symptoms by looking at the left side of the screen.
Under each cause column, you will see either 'exposed' meaning the person has been exposed to that possible cause, 'unexposed' or '?'. The '?' means you don't know whether the person has been exposed or not.
To guess a cause, you click on a column header in the middle table. Before you make a guess, you may want to learn more information. If you see that there is a question mark associated with a person in a column and you would like to know whether the person was exposed to the cause at the head of the column, then click on that question mark.
If the Number of Causes is set to 1, then you need to identify just one cause for the symptoms. It two or more causes, find the causes whose logical OR exactly matches the symptoms. For example if two causes are responsible then if the person surveyed has been exposed to either cause, he or she will acquire symptoms within the delay period (Days till Symptoms Show) with the probability specified (Probability that Symptoms Show).
To pose a question, click on a question mark. You will see the answer. Remember you can ask five questions per day. Hence, best time to take a guess is after asking 4 questions.
To guess a cause, click on the column header in the middle table corresponding to a cause. Remember that guessing a cause causes the game day to end (even if correct). It takes one night to eliminate that source.