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Statistics - Coggle Diagram
Statistics
Research Design
Two types of quantitative research design:
- Experimental
- Observational
Experimental design requires:
- Intervention group
- Control group
-Random allocation
Observation Studies:
- Based on observing what happens
- Correlational (summaries association between variables) or descriptive (summarise basic facts)
Observational Units:
- Observational unit: object being sampled (usually a person, but not necessarily)
- Observation : Raw data collected from the observational unit
Research Question:
- Research questions usually focus on:
- Assessing differences between groups and across times in the same groups.
- Establishing relationship between variables.
Practical Steps for data analysis:
- Data needs to be prepared for computer entry
- Data needs to be entered into a computer, stored and managed,
- Data needs to be summarised and analysed to inform the research questions and draw conclusions for the study.
Data Management:
- Stages of Data Management:
- Coding
- Database or spreadsheet design
- Data entry and/ or transfer
- Data cleaning(invalid response code, missing data, duplicate data)
- Security and subject confidentially
Data Coding:
- Coding converts collected information into a suitable format for easy data entry and statistical analysis
- Coding mostly converts text responses to numerical responses
- Coding manual defines the coding system used.
Coding Manual:
- Integral part of data collection and management
- Especially important in large studies involving different people.
- Should contain the definition of each variable, range of expected responses, format and instruction for recording data, instruction for removing uncertainty, recording of decision regarding coding
Study Design
Randomised Controlled Trial:
- Successful implementation of a randomisation scheme depending on making sure that those responsible for recruiting and allocating participants to the trial have no prior knowledge about which intervention they will receive. This is called allocation concealment.
Longitudinal and Cross-Sectional Studies:
- A cross-sectional study is carried out at just one point in time or over a short period of time. Provide estimates of the features of a community at just one point in time, they are suitable for measuring prevalence but not incidence of disease
- In a longitudinal study individuals are followed over time, which makes it possible to measure the incidence of disease and easier to study the natural history of disease.
Case-control studies:
- In a case-control study the sampling is carried out according to disease rather the exposure status.
Cohort Study:
- A study design where one or more samples ( called cohorts) are followed prospectively and subsequent status evaluation with respect to a disease or outcome are conducted to determine which initial participant exposure characteristics ( risk factors ) are associated with it.
Quasi-experimental Research:
- Quasi-experimental research is research that resembles experimental research but it not true experimental research. Although the independent variable is manipulated, participants are not randomly assigned to conditions or order of conditions.
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Population and samples
- Collect data on a sample from a much larger group called the population.
- Results from this sample are used to infer the results from the entire unknown population.
- For results to be valid sample needs to accurately reflect characteristics of population.
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Categorical Data
- Binary Data: Two groups only, groups are mutually exclusive(i.e value can only be in one group)
- Nominal: more than 2 groups classified by name. Every value has to fit into only one group.
- Ordinal: Same as nominal data except that the groups have a natural and meaningful full order
- Interval Data: Same as ordinal data except that the size of the intervals between groups is equal and meaningful.
The study of the collection, organisation, analysis, interpretation and presentation of data