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1 34 Exercise and mental health A researcher is interested in the e ects of exercise on mental health and he proposes the following study Use strati ed random sampling to ensure representative proportions of 18 30 31 40 and 41 55 year olds from the population Next randomly assign half the subjects from each age group to exercise twice a week and instruct the rest not to exercise Conduct a mental health exam at the beginning and at the end of the study and compare the results a What type of study is this This type of study is a prospective study that utilizes strati ed random sampling block controlled experiments Justi cation because the participants are split into two groups that are mutually exclusive at random Because there are two sectors in each groups one for rest and non exercise it is a controlled experiment Next are the subjects in the treatment group who work out twice a week The percentage of people in the ages of 18 30 31 40 and 41 55 make up the blocking variable b What are the treatment and control groups in this study Treatment Group Subjects who exercise twice a week Control Group Subjects who rest and not exercise c Does this study make use of blocking If so what is the blocking variable Yes The study makes use of blocking the variable being used would be age Ages such as 18 30 31 40 and 41 55 d Does this study make use of blinding What is Blinding This Experiment doesn t utilize this variable Due to all three involved being aware of its objective e Comment on whether or not the results of the study can be used to establish a causal relationship between exercise and mental health and indicate whether or not the conclusions can be generalized to the population at large Based on the fact that this is a well designed controlled randomized trial the ndings of the study can be utilized to establish a causal association between physical activity and mental health Because the sample was chosen using the Strati ed Sampling Technique and the Simple Random Sample the conclusion can be extrapolated to the en tire population by utilizing this method which shows a proper correlation to a randomized version of participants to study f Suppose you are given the task of determining if this proposed study should get funding Would you have any reservations about the study proposal Because both the researcher and the participant are aware of which individual is assigned to which group it is highly likely that the conclusions of the study will be skewed This is because the researcher is aware of which group the participant is assigned to Double blind research must be carried out which means that neither the researcher nor the participant will be aware of which participant is assigned to which group This is a requirement for the research to be considered adequate It is essential that we do this in order to remove any uncertainties that we may have concerning the concept of the study 1 42 Screens teens and psychological well being In a study of three nationally representative large scale data sets from Ireland the United States and the United Kingdom n 17 247 teenagers between the ages of 12 to 15 were asked to keep a diary of their screen time and answer questions about how they felt or acted The answers to these questions were then used to compute a psychological well being score Additional data were collected and included in the analysis such as each child s sex and age and on the mother s education ethnicity psychological distress and employment The study concluded that there is little clear cut evidence that screen time decreases adolescent well being 35 a What type of study is this This is a prospective Observational Study b Identify the explanatory variable The explanatory variable in this study is screen time MAIN VARIABLE Screen Time This variable captures the amount of time teenagers spend on screens It is a key factor of interest as it is hypothesized to have potential associations with psychological well being Age and sex of the child These demographic factors are important since gender and developmental stage can have an impact on psychological well being The mother s educational attainment is taken into consideration since it may serve as a proxy for her socioeconomic standing which in turn may have an impact on the wellbeing of her kid Mother s Ethnicity Ethnicity is taken into account because it may affect psychological well being by contributing to cultural variances The psychological distress of the mother is taken into consideration since it has the potential to impact the family dynamic and in turn the adolescent s overall wellbeing The employment position of the mother is a significant factor to consider as it can impact family relationships resources and the amount of time parents have to devote to their children s upbringing c Identify the response variable The response variable would be the adolescents well being What is the response variable Researchers are interested in studying and evaluating the response variable which is the outcome or characteristic that they are going to be looking at d Comment on whether the results of the study can be generalized to the population and why According to the study three big datasets that are nationally representative were used This suggests that the researchers tried to get a diverse group of teenagers from Ireland the US and the UK Nationally representative means that the results were meant to be representative of the whole people in each country However the real generalizability depends on how well the participants were chosen through sampling So I would say yes e Comment on whether the results of the study can be used to establish causal relationships Because the study was based on observations it is hard to say what caused what Researchers did not change any of the variables so it is hard to say for sure that changes in mental health were caused by computer time or other factors that were measured To prove causation researchers would have to do a controlled experiment in which they change screen time while keeping all other factors the same Because there was no experimental control it is hard to rule out other possible causes and variables that could be messing up the results 2 2 Associations Indicate which of the plots show a a positive association b a negative association or c no association Also determine if the positive and negative associations are linear or nonlinear Each part may refer to more than one plot 1

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