PT106 · S1 · Q21 Psychologist: Some astrologers

When Necessary Assumption answers rule out an idea with "not / no", we should carefully consider them, since many correct answers are written that way. If we negate this and say, "Astrologers have subjected their claims to rigorous experimentation", does that weaken? No. It would weaken if we knew that the astrologers' claims were subjected to rigorous experimentation and were verified by that experimentation. But simply being subjected to rigorous experimentation doesn't weaken the argument.

The author thinks that horoscopes don't determine our personalities. He probably thinks that other stuff determines our personalities -- our family members / our friends / our environment. So, it's very likely that the author thinks that cultural differences between Toronto and New York are part of what explains the personality differences between the two individuals. If we negated this answer and said, "the personality differences can be explained by the cultural differences between the two different cities", that would just strengthen the author's argument. That would show that personality differences were not completely explained by horoscopes.

We don't need for both hospitals to have kept records of 100% of babies over the past 40 years. If one of them only kept records for 99.9% of babies over the past 40 years, would that weaken this argument? No. As long as the birth records on these two individuals are correct (same date / same time), the author has all he needs from the hospital records.

The remark about identical twins is a concession to astrologers. It plays no role in the author's argument, so the author isn't making any assumptions about identical twins. Would it matter if identical twins were only 99.9% genetically similar? No, that wouldn't do anything to the author's argument. Would it matter is identical twins usually have fairy distinct home environments? Nope.