Question

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Classify the experiments according to their experimental designs. Some designs may be used more than once. Vitamins. A sample of 50 children was separated into boys and girls. The members of each group were randomly assigned to two different vitamin supplements. The responses of each child were recorded at the completion of the experiment. Flu. A sample of 50 flu patients was grouped into pairs of similar individuals based on age and gender. Then, within these pairs, each flu patient was assigned to a different flu medication. After three weeks, the responses of each pair were analyzed to compare the effects of the flu medications. Race car fuel. Twenty race cars were assigned to drive two laps, once with fuel A and once with fuel B. The order of treatments was randomized for each race car. The lap times of each race car were recorded to compare the effects of the two different treatments River water quality. A random sample of 100 rivers was selected in a particular region. To assess the relationship between water quality and invertebrate diversity, the water quality and the count and species identity of all invertebrates in each river were recorded Medical treatments. Eighteen volunteers were randomly assigned to three different medical treatments. At the conclusion of each treatment, the response of each volunteer was measured Race car fuel Vitamins matched pairs design matched pairs desigın River water quality Flu observational study block design (not matched pairs) Medical treatments completely randomized design

Answer 1

In randomized block design, the researcher divides the experimental units into different subgroups, called blocks, such that those units have homogenous traits. The experimental units are randomly assigned to treatments within each block. According to the provided experiment of Vitamins", the subjects of the study, that is 50 children are grouped based on their gender and then randomly assigned to two different vitamins. So, the experiment can be considered as a randomized block design, that is block design (not matched pairs). Matched-pairs experiment can be defined as a design in which different participants under two different conditions are matched based on some certain variables, like age, gender, and IQ An experimental design can be considered as a matched pairs design when each subject is assigned to both the treatment. That is, the responses are recorded from all subjects for both treatment conditions. According to the provided experiment of "Flu”, 50 patients are grouped according to age and gender and different flu medication are applied to the patients randomly in each pair. The responses of each pair were recorded after three weeks. As the subjects are paired according to their age and gender, the experiment can be considered as matched pairs design. According to the provided experiment of Race car fuel", there are 20 cars and the lap time for all cars are recorded for fuel A and fuel B. So, the experiment can be considered as a matched pairs design. In the observational study, the data is collected without disturbing the respondents. According to the provided experiment of “River water quality", the water quality, the count and the species identity of all invertebrates are recorded for 200 randomly selected rivers. That is, the researchers do not apply any condition on the randomly selected rivers before collecting the data. So, the experiment can be considered as an observational study. Completely randomized design studies the effects of one primary factor, which the researcher can manipulate and fix at l-levels. Certain factors are controlled by the researcher in this setting, so they remain fixed. For the remaining factors, the experimental units are randomly assigned to the treatment groups. In the provided experiment of "Medical treatments", 18 volunteers were randomly assigned to 3 treatments before collecting the data. So, the experiment can be considered as a completely randomized design.