Statistics 1 Flashcards
What are clinical trials?
Experiment, set up
What are epidemiological trials?
Observational, natural variables
Define: Population (μ)
Entire collection of units, items or individuals under investigation
Define: Sample
Subset of population which we use to collect information
Define: Variable
Any characteristic or attribute which may vary from 1 unit of the population to another
Define: Observation
A value that a variable has been found to have on a particular individual unit
What do rows and columns represent in spreadsheets?
Row represents a unit
Column represents a variable
Define: Accuracy
Correct conclusion
Define: Precision
Confidence in conclusion
Small errors/variability bewteen observations
What 2 things define precision
Repeatability = can the experiment and measurements (results) be repeated by the same person Reproducibility = can another person reproduce the measurements (results) by the 1st person
What are the 2 types of error?
Sampling errors
Non-sampling errors
Explain sampling errors
= Error in the estimate of some population characteristic - have to extrapolate
Small standard error = high precision but not necessarily high accuracy
What are non-sampling errors?
Mistakes
What are non-response errors?
Non-sampling error
Failure to obtain information from a sampling unit e.g. age
What are measurement errors?
Non-sampling error
For some reason the recorded response differs from the true value
What are data-handling errors?
Non-sampling error
Errors associated with the transcribing of data across mediums of storage
How can non-sampling errors be avoided/minimised?
By good study design
Name the 2 types of variable
Qualitative variable = characteristics
Quantitative variable = numerical
Explain what is meant by qualitative variable
Finite number of levels e.g. M/F, employed/unemployed
Levels have assigned numbers
Name 2 branches of qualitative variables
Ordinal
Nominal
What is a ordinal variable?
Variables have a natural ordering
e.g. BP = low/normal/high
Coding of levels are in an order
What is a nominal variable?
Variables have no natural ordering
e.g. blood group = O, A, B, AB
Variables do not have to be written in a specific order
Name the 2 branches of quantitative variables
Discrete
Continuous
What is a discrete variable?
Variable has upper and lower limits
Only a certain number of possible variables
Doesn’t have to be an integer
What is a continuous variable?
Unlimited number of possible variables
Could be measured to any number of decimal place
