Prompted by other discussions on this forum and some surprising contest results I tried to investigate whether contest entrants are teams or individuals. One result is shown in the chart below,

This is a histogram from Contest 23 of the time taken to correctly submit Q1 and Q2.
In orange bars are the times of for each entrant to answer the first question. For example 4 contestants submitted their first correct answer in the 6th minute.
In grey bars is the time between each entrant's first and second correct submission, this is the time to answer the second question after doing the first question.

For the first question there are no correct submissions in the first few minutes, then the rate builds up. For the second question there are many submissions starting from straight after the first question. In fact 73 second submissions take less than 5 minutes and only 2 first submissions take that time.
Since Q1 is "Easy" and Q2 is "Medium" we could reasonably expect that the second question would on average take longer.
A likely explanation is that the best performers are teams who can work on Q2 in parallel with Q1 and submit whichever question is completed first, which is often around the same time.

It's important to be aware of this and individuals shoudn't get disheartened by their rankings, competing only against other individuals they would be higher.
Also any employer using a contest ranking as a basis to interview or hire needs to be very careful.

Very happy to hear comments.

A bit more on the methodology (maybe boring for most so stop here and just take away the points above)

• I also looked at contests 21, 22 and 24. There were always more second questions than first questions answered within 3 minutes. No first question was answered in less than 2 minutes.
• Contest 23 is the best example and the shape of the graph above is different for the different contests but it always starts the same - more grey than orange.
• The times exclude penalties for wrong submissions, they are just times to make a correct submission.
• The total count of entrants who correctly submitted at least Q1 and Q2 was 872
• First submission in 87% cases is Q1 but I allow "First qn" to be Q2 and and second Q1
  in the chart. Note that I only look at these, ignoring Q3 and Q4.