In a 2018 study published in the New Zealand Medical Journal, researchers sought to examine the link between milk consumption and obesity in children from 2 to 4 years of age. Parents of young children were recruited to take part in the study using a variety of different techniques (e.g., direct emailing of families with young children, press releases to media outlets, flyers posted in early childhood education centers, etc.). A total of 1,329 families ultimately enrolled in the study, and each family completed a questionnaire about their child's milk consumption, eating habits, and medical history. Weight and height were also measured for each child, and a body mass index (or BMI) was calculated for each child. One finding of the study was that children who were determined to be overweight, based on their BMI measurement, were more likely to have diets that involved drinking low- or reduced-fat milk, as opposed to drinking whole-fat milk. 1. Would the study described above be considered an experiment or an observational study? Please explain. 2. Regardless of whether a study is an experiment or an observational study, we can classify particular variables involved in the study as being explanatory variables or response variables. In the study described above, if the researchers believe that BMI is affected by the type of milk consumed, which variable (BMI or type of milk consumed) would be the explanatory variable, and which variable would be the response variable? Please explain. 3. Back in Chapter 2, you learned about different types of sampling methods. Based on what you know about how families were recruited to take part in this study, what type of sampling method do you believe these researchers were using? 4. This study involved a large sample (n = 1,329) of children. Can we therefore conclude, because a relationship was noted between the type of milk consumed and obesity, that the type of milk consumed (i.e., low- or reduced-fat versus whole-fat) causes obesity in children? Please explain why or why not. 5. The researchers mention that one limitation of their study is that the type of milk consumed by the children in the study was reported by their parents or caregivers and not assessed directly. If the parents or caregivers did not accurately report the type of milk consumed when completing the questionnaires, we'd say we have a __________________ error. Part 2: More research on milk consumption In a 2021, a study published in the American Journal of Clinical Nutrition sought to examine whether whole-fat milk is as good for children as low-fat milk. In this study, a sample of 49 Australian children between the ages of 4 and 6 years old were followed for three months. Each child was randomly assigned to consume, on a daily basis, either low-fat milk or whole-fat milk. The milk was delivered to the children's homes each night to ensure that their parents did not have to pay for the milk, and the milk was presented in plain packaging so that neither the parents nor the children knew if they were consuming low-fat or whole-fat milk. At the start of the study, measurements were taken of each child's body mass index (or BMI), blood pressure, and general cardiovascular health. The same measurements were taken at the end of the study, after three months of daily consumption of either low-fat or whole-fat milk. The researchers observed no significant differences between the low-fat and whole-fat milk groups in terms of cardiovascular health or measures of obesity. 6. What is the explanatory variable in this study? 7. What is/are the response variable(s) in this study? 8. The description above does not say how the 49 children were selected to take part in this study. Why would it be important to know this information? 9. Why was it important for the researchers to randomly assign the children to consume either low-fat or whole-fat milk? 10. One principle of experimental design is to use enough subjects. In your opinion, is 49 subjects enough? Please explain. 11. Suppose you learn that the amount of milk consumed by children each day was not controlled for. Since "amount of milk consumed" is a variable that could impact the response and get mixed up with "type of milk consumed," we would call "amount of milk consumed" a ____________________ variable. 12. It turns out that because the milk was delivered to each house in plain packaging, the researchers did not know who was consuming which type of milk. When neither the researchers nor the participants know who is getting which treatment, we say we have a _______________________________ study. 13. Interestingly, the study described in Part 1 of this lab activity reported that children who consumed low-fat milk were more likely to be overweight than the children who consumed whole-fat milk. The study reported here in Part 2 observed no significant differences in obesity between those who consumed low-fat milk and those who consumed whole-fat milk. In your opinion, what is one thing that might explain why these results were so different? 14. Given what you know about the two studies (i.e., the study described in Part 1 and the study described here in Part 2), would you trust the results of one study more than the other? Please explain. Part 3: More big ideas Before the start of flu season, some individuals who were getting vaccinated for COVID-19 were asked if they wanted to receive a flu shot at the same time as their second dose of the COVID-19 vaccine. Naturally, this begs the question of possible side effects when it comes to receiving these shots simultaneously. In a study conducted in Great Britain, 679 volunteers who were receiving a COVID-19 vaccine participated in an experiment. All participants received their first COVID-19 dose in the normal way and agreed to receive a flu shot upon returning to receive their second COVID-19 dose. When participants returned to receive their second dose, half of the participants were randomly assigned to receive a flu shot at the same time, while the other half received a placebo. According to the researchers, the side effects in the participants who were given the flu shot at the same time as their second COVID-19 dose were mild to moderate. Further, through an examination of blood samples, the researchers observed that getting the flu shot and the vaccine simultaneously did not appear to change the effectiveness of these shots when compared to getting each one separately. 15. Based on the study description above, what do you think it means when we say the other half of the participants received a placebo, and why might a placebo have been used in this study? A botanist is attempting to learn about a new species of plant. She wants to better understand how watering frequency (either daily watering or weekly watering) and sunlight (either low sunlight or high sunlight) affect the growth of this species of plant. She randomly assigns several plants of the species to receive either daily or weekly watering. The plants are also randomly assigned to be kept in areas that receive either low sunlight or high sunlight. After 8 weeks, the growth of each plant is measured. 16. Upon reading the above description of the plant study, George says that four treatments were involved in the study, but Avery believes only two treatments were involved in the study. Who is correct? Please explain.

This is a big