4.41 No. Rich nations have more TV sets than poor nations. Rich nations also have longer life expectancies because they have better nutrition, clean water, and better health care. There is common response relationship between TV sets and length of life.
4.42 In this case, there may be a causative effect, but in the direction opposite to the one suggested: People who are overweight are more likely to be on diets, and so choose artificial sweeteners over sugar. (Also, heavier people are at a higher risk to develop diabetes; if they do, they are likely to switch to artificial sweeteners.)
4.43 No. The number of hours standing up is a confounding variable in this case. The diagram below illustrates the confounding between exposure to chemicals and standing up.
4.44 Well-off people tend to have more cars. They also tend to live longer, probably because they are better educated, take better care of themselves, and get better medical care. The cars have nothing to do with it. The relationship between number of cars and length of life is common response.
4.45 It could be that children with lower intelligence watch many hours of television and get lower grades as well. It could be that children from lower socio-economic households where parents are less likely to limit television viewing and are unable to help their children with their schoolwork because the parents themselves lack education. The variables “number of hours watching television” and “grade point average” change in common response to “socio-economic status” or “IQ”.
4.46 Single men tend to have a different value system than married men. They have many interests, but getting married and earning a substantial amount of money are not among their top priorities. Confounding is the best term to describe the relationship between marital status and income.