Les Roberts answers questions about Lancet study

The BBC has Les Robert's answers to questions sent in by readers. Some extracts:

A research team have asserted in an article in Science that the second Lancet study is seriously flawed due to "main street bias."

We worked hard in Iraq to have every street segment have an equal chance of being selected. We worked hard to have each separate house have an equal chance of being selected. Realize, there would have to be both a systematic selection of one kind of street by our process and a radically different rate of death on that kind of street in order to skew our results. We see no evidence of either.

Madelyn Hicks, a psychiatrist and public health researcher at King's College London in the UK, says she "simply cannot believe" the paper's claim that 40 consecutive houses were surveyed in a single day.

In Iraq in 2004, the surveys took about twice as long and it usually took a two-person team about three hours to interview a 30-house cluster. I remember one rural cluster that took about six hours and we got back after dark. Nonetheless, Dr. Hicks' concerns are not valid as many days one team interviewed two clusters in 2004.