Question

In elementary school (grades 1 to 6 ), there is a strong association between a child's height and the child's reading ability. Taller children tend to be able to read at a higher level. However, there is a very significant confounding variable that is influencing both height and reading ability. What is it?

Short answer

The confounding variable influencing both a child's height and reading skills is the child's Age.

Step-by-step solution

Understanding Confounding Variable

A confounding variable links with both the dependent and the independent variable, causing a spurious association. Confounding Variable confuses the effect one variable could have on another. In this case, one needs to find out the common variable, impacting both a child's height and reading ability.

Analyzing variables

The height of a child increases with age and so does their reading ability, as one grows older, they learn more about vocabulary and linguistics, improving their reading ability. Though it seems that height (which increases with age) randomly could influence reading ability, in reality, both vary with age. That’s where the confounding effect comes into the picture. That means the height doesn't actually cause better reading ability.

Uncovering the Confounding Variable

Upon careful consideration of the factors influencing a child's height and reading ability, one can deduce that the child's age could be the confounding variable. Age affects growth and development (including height), and increased age also signifies more exposure to education and hence, better reading ability, in general.