Please help me answer these questions. Thank you!

Consider the population of children ages 6 10 who attend public schools. How could a representative sample of this population be obtained? Identify the prob- lems with using the following methods to obtain a sample of this population: a. Send a survey (with a stamped return envelope) to every public elementary schooL The students who return the survey are the sample. b. The investigator has worked with educational leaders in states in the Southeast and knows that the schools in this region will be motivated to participate. The investigator collects data only on children from these schools. c. Children attending elementary schools with high test scores may be more likely to participate, so the investigator chooses only children from schools in the top 10%. d. The investigator conducts a random sample using home telephone number of parents with children ages 6 10 in public schools. Describe a scenario when it would be preferable to present the distribution with a count on the vertical axis? With a proportion