possess upon entering kindergarten were not imposed on them by the researcher. There are four people in a family-a father, a mother and two children-and they have won two tickets to go to Disneyland for a week. They decide to select a sample of two people for the trip as follows. The mother and father flip a coin to see which of the two of them will go, and they then flip a coin to see which of the two children will go. This is a. a simple random sample of size two from the family since two coins were flipped. b. a probability sample from the family since each member of the family has a known chance of being selected to go on the trip. c. not a probability sample since the mother and father can't go together. b. This is correct. The chance of each person in the family going is 1/2 (the chance that their coin comes up favoring them), so that each person in the population has a known chance to be selected. This is the definition of a probability sample.
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Researchers are studying the absorption of two drugs into the bloodstream. Each drug is to be injected at three dosages. There are 24 people in the study, and they are randomly divided into six groups. Each of the six groups is randomly assigned to a different drug and dosage combination. After 30 minutes the concentration of drugs in a subject's blood is determined. Which of the following is correct?
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A statistics instructor wants to know which route will get her to school the fastest. Each day from October 2 to November 15, when she gets to the turn point she checks the odometer on her car. If it shows an even number she takes the freeway; if it shows an odd number, she takes the in-town route. She records the total time each day. What is the explanatory variable in this study?