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Lesson 3.9 Using Studies Wisely

Objectives Identify when it is appropriate to use information from a sample to make an inference about a population and when it is appropriate to make an inference about cause and effect. Evaluate if a statistical study has been carried out in an ethical manner.

Important ideas from the text Inference: a conclusion reached on the basis of evidence and reasoning

Random sample Using a chance process to pick members from population Why do we take them? So our sample is representative of population What conclusion can be made? Inference about the population: generalize results to whole population

Random assignment Subjects assigned to treatments using chance process Why do we do it? Create groups roughly equivalent What conclusion can be made? Inference about cause and effect: one variable causes changes in the other

Practice

Example 1 Get all the students in your statistics class to participate in a study. Ask them whether or not they study with music on and divide them into two groups based on their answer to this question. Random Sample? NO Random Assignment? NO Conclusion: Can’t make inference about population Can’t make inference about cause and effect No conclusion!

Example 2 Select a random sample of students from your school to participate in a study. Ask them whether or not they study with music on and divide them into two groups based on their answer to this question. Random Sample? YES Random Assignment? NO Conclusion: Can make inference about population Can’t make inference about cause and effect Students in the whole school have lower GPA if they listen to music, but we can’t say causation

Example 3 Get all the students in your statistics class to participate in a study. Randomly assign half of the students to listen to music while studying for the entire semester and have the remaining half abstain from listening to music while studying. Random Sample? NO Random Assignment? YES Conclusion: Can’t make inference about population Can make inference about cause and effect Listening to music causes GPA to go down, but only for students in our statistics class

Example 4 Select a random sample of students from your school to participate in a study. Randomly assign half of the students to listen to music while studying for the entire semester and have the remaining half abstain from listening to music while studying. Random Sample? YES Random Assignment? YES Conclusion: Can make inference about population Can make inference about cause and effect Listening to music causes GPA to go down, for all students in the whole school

Principles of data ethics Institutional review board Informed consent Confidentiality

Example Will people try to stop someone from driving drunk? A television news program hired an actor to play a drunk driver and used a hidden camera to record the behavior of individuals who encountered the driver. Was this study carried out ethically? Explain.