Describe the selection bias likely to exist in the following situations:

a. A study of 3,600 children in Australia found that the children who slept early and woke up early had a lower BMI as compared to children who slept late and woke up late. Therefore, children who are early sleepers are healthier than children who go to sleep late.

b. A study of 1,500 college students found that students who studied in a private school scored better in the first year of college than students who studied in a government-aided school. Therefore, an education from a private school will improve a student’s academic performance.

c. A study of 2,500 women in Sweden found that women who play computer games for an hour or more every day have a higher chance to become obese than ones who do not play them at all. Therefore, women who play computer games have a higher tendency to become obese.