No, the sample population of just asking Andrea's five best friends if they are coming to her birthday party is not the best representation of the whole class. This is because her five best friends may not be representative of the entire class. There could be other students in the class who have different interests, schedules, and priorities than Andrea's five best friends. As a result, the responses from Andrea's five best friends may not accurately reflect the opinions and intentions of the entire class.
A better approach would be to randomly select a sample of students from the class and ask them if they are coming to Andrea's birthday party. This way, the sample would be more representative of the entire class and the responses would be more likely to reflect the opinions and intentions of the whole group. Ideally, the sample should be large enough to ensure statistical significance and minimize the margin of error.
In summary, while asking Andrea's five best friends may be convenient and quick, it is not the best approach to determine how many people will come to her birthday party. A random sample of the class would provide a more accurate estimate of the expected attendance.