Question

After you complete your survey of students reported heights at your school, you discover that your sample is biased. Exactly 10% of the students in your sample tended to over report their height more than the average student in the general population at the school. What conclusion can you reach about the mean of the average difference in your sample?

It is greater than the mean of the average difference of the population
It is less than the mean of the average difference of the population
It is exactly 10% greater than the mean of the average difference of the population
It is exactly 10% less than the mean of the average difference of the population