A journalist's headline has reported, "Folic acid tied to better toddler talk".

a. What kind of claim is this? Frequency, association, or cause?

Here is a summary of the main finding:

Women who took folic acid supplements in the first two months of pregnancy were less likely to have kids with severe language delays in a new study from Norway.

b. Given this summary, what are the variables in this study?

Here are some of the methodological details:

The researchers gave surveys to close to 40,000 Norwegian women a few months into their pregnancies. Those included questions on what supplements women were taking in the four weeks before they got pregnant through eight weeks after conception.

Then, when their kids were three years old, Susser and his colleagues asked the same women about kids' language skills, including how many words they could string together in a phrase.

c. The information above can help you interrogate construct validity. How well does it seem they measured their variables?

Finally, consider this comment:

The pattern remained after Susser's team took into account other factors that were linked to both folic acid supplementation and language skills, such as a mom's weight and education, and whether or not she was married.

d. If you've read Chapter 8, you can probably figure out what this means. Explain, in your own words, how the researchers can "take into account" these other factors.