@nprofile1q... by number or by salience? Large MNC are very big and visible in the economy. I note the survey doesn't actually ask the general public to estimate the profitability of your local greengrocer.
More to the point I don't think the general public has much of a handle on company profit/revenue ratios as is clear from the range and realism of the answers.
As a former economist maybe I ought to have a better handlle on this, but I don't have much of a clue either, except knowing that supermarkets only have a P/R in low single digits. I would be inclined to decline to attempt to come up with figures if were to be asked by the IEA but I suspect most people just make a wild guess based on how exploitative they feel a particular industry seems.
But then current economic orthodoxy is based on the assumption that all economic actors have perfect knowledge (not true, of course), so setting up a survey like this is consistent with that viewpoint, especially as it can then be then used to attempt to justify their partisan lobbying against increasing corporate tax and stamping out avoidance.