Effect of Sample Size
Study the occurrence of a hereditary trait with simple pattern of dominant and recessive genetic inheritance in a large population.
Students poll at least 100 students in the school (depending on the size of your school, you may decide to poll just your grade, or several classes, or even the whole school). Questions you can ask: A. Are you right or left handed? Or B. Can you roll your tongue?
Figure the percentage of the population which displays each trait. The theoretical percentages would be 75% right handed, 25% left handed; and 75% capable of rolling tongue, 25% incapable.
We will use this in the discussion when we talk about the benefits of using a larger sample when looking at probability of inheriting a trait.
Inheriting genes from your parents involves chance. Students should have some idea of what probability means. For example, there is a fifty-fifty chance of having a girl each time you have a baby. Just because a family already has 5 boys doesn't mean that the next baby has to be a girl ö the chance is still 50-50.
Provide each student with a penny. Have them toss it 10 times and graph the results. How many students have exactly half heads and half tails? Now cumulatively take the results they got and graph them together as a class. Are the results closer to 50-50? Discuss that having a larger population sample is necessary for probability and statistics to be valid.