Practice translating scientific hypotheses into statistical terms
Design statistical analysis plans to evaluate hypotheses, including specification of variables, models, and specifics of how any hypotheses will be evaluated
For each study presented, define the variables and parameters of interest in any model. Specify appropriate null and alternative hypotheses and a strategy for hypothesis testing (this may include one hypothesis test or a series of hypothesis tests, in which case you should provide the null and alternative hypotheses for each test conducted). If your hypothesis testing strategy involves a statistical model, be sure to identify the outcome variable and any predictor variables included in the model. Each study is inspired by research in top public health and medical journals, though details of each study may have been altered for the sake of simplicity and time.
Researchers are interested in whether sexual minority youth are at different risk of physical dating violence compared to their majority counterparts. They have recruited 100 sexual minority youth and 75 sexual majority youth and have asked all youth whether they have ever experienced physical dating violence (reported as a binary variable with values yes or no). Of the study participants, 65% report their biological sex as female, and 35% report as male. Researchers are not sure whether the association between sexual minority status and physical dating violence is the same for each biological sex or not.
Adolescents participating in a large, population-representative study were asked (1) whether they had a friend who tried to commit suicide in the past year, and (2) how many times they personally tried to commit suicide in the past year. The response to question (1) was a binary variable (yes/no), and the response to question (2) was a count, with most adolescents reporting 0 suicide attempts; other report options were 1, 2, 3, 4+ (the last category combined all those reporting four or more attempts due to the very small number of adolescents in these categories). Researchers wish to know whether the presence of a friend who tried to commit suicide was associated with the count of personal suicide attempts.
Researchers were interested in whether receipt of palliative care after diagnosis of advanced cancer might affect medical costs. Eligible patients had been diagnosed with advanced terminal cancer and had an expected lifespan of at least 3 months. The outcome was defined as total health care costs from diagnosis to six months after diagnosis. In addition to the binary indicator of whether palliative care was received by the patient, the researchers wanted to control for the patient’s gender, marital status (married or not), poverty level (living in extreme poverty, living in poverty, not living in poverty), and residence (urban or rural).
Researchers in Syria and the US designed an internet-based survey using social media platforms. This survey targeted adults who were able to read and understand Arabic and had access to the internet, and the survey was administered to individuals from all 22 Arab league countries between December 26, 2020 and January 14, 2021.
Vaccine acceptance was measured by asking survey respondents if they would be willing to get the COVID-19 vaccine if it were freely available (yes, or no). The researchers wanted to understand factors related to vaccine acceptance, if the vaccine were to become available free charge, in order to target interventions to increase immunization rates. The factors they wanted to evaluate include World Bank income level of the respondent’s country (high income, upper middle income, lower middle income, or low income), gender (measured as binary), age, education (less than high school, high school, university, graduate school), place of residence (inside or outside home country), prior COVID-19 infection (yes or no), and family death due to COVID-19 (yes or no). Because many respondents were living in areas with active armed conflicts, researchers also wanted to know whether living in a conflict-ridden area affected the association between the factors of interest and vaccine acceptance.
Researchers wish to determine whether indoor noise from traffic at night (i.e., levels of traffic noise in decibels from nearby roads measured in bedrooms) is associated with systolic blood pressure (measured in mm Hg). When evaluating this association, they want to be careful to control for potential effects of traffic-related air pollution (measured as ppm CO) on systolic blood pressure, given that traffic-related air pollution and traffic noise may be closely related.