Answer to Question 1
a. Girls tend to take fewer math courses than boys do, and those courses may be at lower levels. On the other hand, girls might take fewer courses in math because they tend not to be as inherently proficient; there does not seem to be any evidence to support this.
b. Boys have traditionally scored higher on the SAT-Math than girls do. Some have concluded that boys have better math reasoning abilities. On the other hand, objective standardized tests may not really be good at spotting math reasoning ability; these tests also don't predict grades in later math classes very well.
c. Some researchers have concluded that the higher testosterone levels in men are responsible for the higher math proficiency. Unfortunately, these researchers didn't measure those hormone levels in the students they observed. There is also no demonstrated connection between testosterone level and math ability in any case.
d. In some circumstances, a stereotype threat based on expectations may affect females' performance on math problems.
e. Recently, the gap in math test scores between women and men has gotten smaller, and it isn't very big to begin with. Greater emphasis on female performance in math may be exerting an effect.
Answer to Question 2
In this study, parents with myopia might be more likely to use night lights. Because myopia has a genetic component, the result might have been that people whose children were predisposed to nearsightedness used night lights. The lights may have been irrelevant.
The sample used in the study consisted of children in families who used an eye clinic. It is not clear that the sample was represented of children in general.
The study was retrospective, requiring parents to remember what they had done when their children were infants. This was an average of six years prior to the study, so memories may have been inaccurate.