Research Design PDF

Feature Cross-Sectional Case-Control Study Cohort Study Study Study Observational, data Observational, compares Observational, follows a Design collected at a single cases and controls group over time...

Feature Cross-Sectional Case-Control Study Cohort Study Study Study Observational, data Observational, compares Observational, follows a Design collected at a single cases and controls group over time point in time (retrospective) (prospective or retrospective) Data Data collected once at Data collected by looking Data collected over a Collection a single time point back at past period of time from an exposures/events exposed group Purpose To determine To identify risk factors or To determine the effect prevalence or what is causes by comparing of exposures on happening at the exposure in cases vs. outcomes over time moment controls Time Frame Single point in time Retrospective (looking Prospective (future) or (snapshot) back at past data) retrospective (past data) Example What is the What factors contributed to What is the long-term Question prevalence of diabetes the development of lung effect of smoking on in a population? cancer in smokers? lung cancer risk? Type of Data Descriptive Analytic (comparing Analytic (tracking (prevalence, exposures between cases changes over time characteristics) and controls) between exposed and non-exposed) Strengths Fast, cost-effective, Efficient for studying rare Good for understanding provides a snapshot of diseases or outcomes, causality, can assess the population good for hypothesis multiple outcomes generation Weaknesses Cannot determine Cannot establish causality, Time-consuming, causality, no temporal subject to recall and expensive, potential loss data selection bias to follow-up Establish No, only associations No, only associations Yes (prospective), can Causality? suggest causal relationships  Data Descriptive statistics Comparison of exposure Comparison of Analysis (e.g., prevalence rates between cases and outcomes in exposed rates) controls vs. non-exposed groups over time Typical Use Population health Studying rare diseases, Studying long-term surveys, prevalence identifying risk factors health outcomes, risk studies factors, cohort comparisons Example Scenarios: Cross-Sectional Study: A survey in a city to determine how many people currently have hypertension and identify demographic trends (e.g., age, sex, lifestyle). Case-Control Study: A study comparing lung cancer patients (cases) with healthy individuals (controls) to identify risk factors like smoking history, air pollution exposure, or genetics. Cohort Study: A study following two groups of individuals, smokers and non-smokers, over 10 years to assess the development of lung cancer. This table organizes the core aspects of each study design, helping to differentiate their purpose, data collection methods, and strengths/weaknesses. This handwritten note provides a summary of observational study designs and breaks them down into three types: 1. Cross-Sectional Study Characteristics: ○ Involves a survey or a snapshot of a specific population at one point in time. ○ Suitable for large groups and provides quick results. ○ Data collection: Observes, measures, and collects data once. Uses: ○ Used in epidemiological studies and for prevalence studies. ○ Helps determine current state (e.g., "What is happening right now?"). 2. Case-Control Study Characteristics: ○ Retrospective design (looks back in time). ○ Focuses on people who have a disease or outcome and compares them with those who do not. ○ Used especially for studying rare diseases. Purpose:  ○ To identify exposure factors related to the disease. ○ Uses Odds Ratio (OR) to measure association. OR < 1: Protective effect against the disease. OR > 1: Increased risk. OR = 0: No effect. Process: ○ Analyzes history or previous events through medical records or interviews. 3. Cohort Study Characteristics: ○ Observes people exposed to a risk factor (RF) (e.g., smoking) over time. Types: ○ Prospective Cohort: Tracks exposed individuals into the future to observe outcomes (e.g., lung cancer). ○ Retrospective Cohort: Starts with existing data from the past and follows outcomes (e.g., past insulin use and current health outcomes). Measures: ○ Both Relative Risk (RR) and Odds Ratio (OR) can be calculated. These notes provide a concise comparison of each study design's purpose, characteristics, and typical uses in research. Study Designs with Full Details on Advantages and Disadvantages 1. Case-Control (Retrospective) Studies Description: A study that compares patients who have a disease or outcome of interest (cases) with patients who do not have the disease or outcome (controls). History/previous events of both cases and controls are analyzed by looking back in time (retrospectively) through examination of medical records, interviews to identify a characteristic/risk factor to determine the relationship between the risk factor and the disease. Advantages: ○ Appropriate for examining conditions that develop over a long time.  ○ Useful for investigation of a preliminary hypothesis. ○ Fast and least expensive. Disadvantages: ○ Have the greatest number of possible biases/errors. ○ Depend on high-quality existing records. ○ Challenge in the selection of appropriate control group. Example: There is a suspicion that zinc oxide, the white non-absorbent sunscreen traditionally worn by lifeguards, is more effective at preventing sunburns that lead to skin cancer than absorbent sunscreen lotions. A case-control study was conducted to investigate if exposure to zinc oxide is a more effective skin cancer prevention measure. The study involved comparing a group of former lifeguards that had developed cancer on their cheeks and noses (cases) to a group of lifeguards without this type of cancer (controls) and assess their prior exposure to zinc oxide or absorbent sunscreen lotions. This study would be retrospective in that the former lifeguards would be asked to recall which type of sunscreen they used on their face and approximately how often. This could be either a matched or unmatched study, but efforts would need to be made to ensure that the former lifeguards are of the same average age, and lifeguarded for a similar number of seasons and amount of time per season. 2. Cross-Sectional Studies Description: Data are observed, measured, and collected at one point in time. Also labeled as survey, epidemiological, or prevalence studies. Determine “What is happening?” at that moment. Advantages: ○ Best for determining the status quo of a disease/condition. ○ Quick and relatively inexpensive. Disadvantages: ○ Only provides a snapshot in time which may result in misleading information. ○ Difficult to get a large sample, and the sample may not be representative of the entire population. Example: A medical study investigates the prevalence of breast cancer in a population. The researcher can look at a wide range of ages, ethnicities, and social backgrounds. If a significant number of women from a certain social background are found to have the disease, then the researcher can investigate further. 3. Cohort Studies (Prospective and Retrospective) Description: A cohort refers to a group of people who share something in common and remain part of a group over an extended time. In a cohort study, a particular group with a  certain characteristic is observed over a certain period of time. Addresses “What will happen?” (prospective) or “What had contributed to the problem?” (retrospective). Advantages: ○ Appropriate for studying the causes of a condition, the course of a disease, or risk factors. ○ Possesses the correct time sequence to provide strong evidence for possible causes/effects. Disadvantages: ○ Extended study period results in large costs. ○ Other events occurring during the study period may have affected outcomes. ○ Susceptible to problems in patient follow-up and dropout. 4. Experimental Studies Description: Experimental studies that involve humans are known as clinical trials. Controlled clinical trials are studies whereby an experimental drug or procedure is compared with another drug/procedure. In randomized clinical trials, subjects are randomized to treatment options providing the best assurance that the result was due to intervention or most rigorous evidence of causality. Advantages: ○ Gold standard against which other studies are judged. ○ Provides the greatest justification for concluding causality and is subject to the least biases. Disadvantages: ○ Costly and time-consuming. ○ Evidence from a clinical trial may not be 100% applicable to current practice as certain factors may have been excluded. Certainly! Here’s a table comparing the different study designs along with their respective descriptions, advantages, disadvantages, and examples: Study Design Description Advantages Disadvantage Example s Case-Control Compares patients - Suitable for - High potential A study (Retrospective with a conditions for comparing ) disease/outcome developing over biases/errors former (cases) to those a long time lifeguards with without it (controls). - Depends on cancer on their Analyzes - Useful for high-quality cheeks and history/previous investigating existing noses (cases) to events by looking preliminary records lifeguards back in time, often hypotheses without cancer using medical - Difficulty (controls), records or - Fast and least selecting assessing prior interviews to expensive controls use of zinc identify risk factors oxide sunscreen and determine vs. absorbent relationships. sunscreen. Former lifeguards are asked to recall their sunscreen type and usage frequency, with efforts made to match age and years of lifeguarding. Cross-Section Observes, - Quick and - Only provides A medical study al measures, and relatively a snapshot, investigating the collects data at one inexpensive potentially prevalence of point in time. Often misleading breast cancer used in surveys or - Best for across various prevalence studies determining the - Difficult to ages, to assess the status quo of a obtain a ethnicities, and current status of a disease/conditio representative social disease/condition. n large sample backgrounds. If a pattern is identified (e.g., a specific social background with higher prevalence), further investigation can be pursued. Cohort Follows a group of - Ideal for - Extended Observing a (Prospective people with a studying causes duration leads group with a and common of a condition, to higher costs certain risk Retrospective) characteristic over disease factor (e.g., time. Observes this progression, or - External smoking) over group for an risk factors events during time to study the extended period to the study may development of examine risk factors - Strong affect a related or the progression time-sequence outcomes disease (e.g., of a condition. for cause/effect lung cancer). Prospective studies - Risk of Prospective ask "What will dropout studies look happen?" while forward, while retrospective retrospective studies explore studies examine "What contributed past exposures to the issue?" by reviewing medical records. Experimental Involves human - Gold standard - Expensive A randomized (Clinical participants, in study designs and clinical trial Trials) commonly as time-consumin comparing a clinical trials. - Provides g new drug with a Controlled trials strongest standard compare an evidence for - Results may treatment to experimental drug causality with not fully apply assess or procedure to minimal biases to real-world effectiveness, another, while practice due to ensuring that randomized trials exclusions the observed allocate subjects effects are due randomly to to the treatment options, intervention and minimizing biases not external and increasing factors. causal evidence. Key Points: 1. Case-Control Study: ○ Involves selecting participants based on the presence or absence of a disease and looking backward to see if they had been exposed to a risk factor. ○ Odds Ratio (OR) is used as the measure of association. Relative Risk (RR) cannot be used because the prevalence is set by the researcher. ○ Often used for rare diseases as it approximates the OR for such cases. 2. Prospective Cohort Study: ○ Participants are initially exposure-defined (exposed vs. unexposed) and followed forward in time to observe the development of the disease. ○ Both Relative Risk (RR) and Odds Ratio (OR) can be calculated in prospective cohort studies. ○ Useful for testing the effect of a new intervention or treatment. 3. Retrospective Cohort Study: ○ Starts with participants based on past exposure data and follows them through historical records to see if they developed the disease. ○ Both RR and OR are relevant measures for retrospective cohort studies. Symbols: Present and Absent symbols represent exposure and disease status. The question mark signifies the information researchers aim to discover, such as the association between exposure and disease. Investigator presence shows when the researcher begins the study (e.g., at the time of exposure in prospective studies, after disease development in case-control studies). This comparison highlights how each study design handles timing, data collection, and the calculation of risk measures. Here is a table based on the image you provided, which compares Non-Experimental, Quasi-Experimental, and Experimental (Randomized Control Trial - RCT) study designs in terms of features and rigor: Study Design Description Comparison Group Rigor Non-Experimental Measures outcomes before and No comparison Low rigor after a program for participants group only. Quasi-Experiment Measures outcomes for program Has a comparison Moderate al participants and non-participants, group rigor but without random assignment. Attempts to "control" for bias. Experimental/RCT Randomly assigns participants to Explicit comparison Highest either a treatment or control group. group with rigor Measures outcomes for both randomization groups. Additional Notes Increasing Rigor: Experimental/RCT designs are the most rigorous, followed by quasi-experimental, then non-experimental. Suitability: While RCTs are highly rigorous, they may not always be feasible due to constraints such as cost, ethics, or practical limitations. Quasi-experimental designs provide an alternative when randomization is not possible, although they are less robust in controlling for biases. Non-experimental designs are the least rigorous and typically used when only observational data is available or for preliminary investigations. This table summarizes different types of research study designs. Here’s a quick overview of each: 1. Experiment  ○ Class: Experimental ○ Type: Longitudinal ○ Protocol: Select a sample, measure baseline parameters, apply intervention, measure outcome over time. ○ Examples: Clinical trials, laboratory experiments (e.g., pesticide testing). 2. Cohort ○ Class: Observational ○ Type: Longitudinal ○ Protocol: Define a cohort, assess outcomes based on exposure or risk factors. ○ Examples: Studying disease progression, evaluating how factors affect health over time. 3. Case-control ○ Class: Observational ○ Type: Longitudinal ○ Protocol: Define cases (people with an outcome) and controls, look for previous exposure. ○ Examples: Studying cancer risk factors, identifying potential risks of certain behaviors. 4. Cross-sectional ○ Class: Observational ○ Type: Cross-sectional ○ Protocol: Define a sample, collect information about the parameter of interest. ○ Examples: Health surveys assessing how common certain conditions are. 5. Repeated cross-sectional ○ Class: Observational ○ Type: Cross-sectional ○ Protocol: Collect information about parameters in different samples over time. ○ Examples: Studying population-level changes like smoking trends. Let me know if you need any additional details or a more detailed analysis of any section! Study Notes Research Design Research involves asking questions and finding answers, like which herbal remedies can be used alongside cancer treatment. Research studies must be conducted ethically to protect participants. Proposals for research studies need to be submitted to an ethical committee. Types of Studies  Quantitative studies focus on the numbers of data (e.g., how many people). Observational studies only observe data without interfering (e.g., observing participants only). Interventional studies involve intervening in the study (e.g., clinical trials). Qualitative studies focus on the best quality data through interviews to get a deeper understanding (e.g., asking open-ended questions about how participants feel). Interviews are used to provide detailed insight. Surveys gather information from a large group, quickly (e.g. snapshot data). Observational Studies Survey: Quick snapshot of data, easy to administer, but can be biased if time frame is too long Case control: Focuses on a specific disease (such as skin cancer), looking back at factors that may have contributed to the disease (retrospective) Cohort: Tracking individuals over time to identify potential causes of disease (prospective). Measures exposures and looks at resulting outcomes. Interventional Studies Clinical trials (RCT/RCCT): Controlled studies comparing different treatments using a sample group receiving one treatment or placebo (another treatment). Participants are randomly assigned to groups (e.g., odd patients get one treatment, even patients get another). Monitors the effect between groups or in a single group over time. Case Control Studies Focus on a specific disease (like Hashimoto's disease) and looking at factors that contribute to it. Evaluates what factors might be connected to, or protect from, the disease. Cross-Sectional Studies Collects data at one specific time point to study the prevalence or distribution of a disease, or other characteristic.  Useful for identifying the presence of a disease in a population at that particular time. Cohort Studies Tracks a group over time (prospective or retrospective) collecting data on exposures and outcomes. Focuses on investigating the causes of a particular condition, or course of a disease. Looks at possible causes of health conditions, or how they cause problems over time with a group of people. Experimental Studies Studies that investigate the impact of a new drug, or procedure. Subjects are randomly assigned to different groups (treatment, control). Tracks the effectiveness of a new treatment or procedure by carefully selecting participants (randomization) and placing them into different treatment and control groups. Related Documents Research Design (2021) PDF Chat with Document Description Explore key concepts in research design, focusing on various types of studies including qualitative and quantitative approaches. Learn about the importance of ethical considerations and how observational and interventional studies are carried out. This quiz is ideal for anyone interested in understanding the foundations of research methodologies.