Define selection bias.
A distortion in results due to non-random selection of participants.
True or false: Confirmation bias leads researchers to favor information that confirms their hypotheses.
TRUE
This bias can skew data interpretation and conclusions.
Fill in the blank: Publication (or reporting) bias occurs when only _______ results are published.
Positive
Failure to publish results from valid studies, often as they showed a negative or uninteresting result.
Important in meta-analyses where studies showing negative results may be excluded.
What is observer bias in studies? Particularly in non-blinded trials.
Also called Expectation bias (Pygmalion effect)
Observers may subconsciously measure or report data in a way that favours the expected study outcome.
Observer bias is also known as the _______effect.
Pygmalion effect
Researcher favouring expected study outcome > than true performance
Pygmalion was a sculptor who fell in love with a statue he had carved.
Define attrition bias.
A bias resulting from participants dropping out of a study.
True or false: Recall bias affects participants’ ability to remember past events accurately.
TRUE
Common in retrospective studies where memory is relied upon.
Fill in the blank: Funding bias can arise when research is influenced by _______.
financial sponsors
How does the Hawthorne effect (or social desirability bias) impact the behaviour of research participants?
It changes their behaviour due to the knowledge that it is being studied
E.g. Similar to when being assessed.
Like wearing a ‘hawthorn’, becoming centre of attention.
A 60-year-old woman participates in a new breast cancer screening programme that utilises an advanced imaging technique to detect tumours earlier than standard mammography.
As a result, she is diagnosed with breast cancer at an earlier stage compared to women using standard mammography.
However, statistical analysis shows that the overall mortality from breast cancer in the screened population remains unchanged compared to the unscreened population.
If a person says that this new test increases survivability and prognosis of breast cancer, what bias are they engaging in?
Lead-time bias
Where they let the ‘time’ (earlier detection) ‘lead’ in their thinking, to think this is a positive intervention, rather than the actual prognosis.
Provide an example of Continuous Data.
- Blood pressure
- Temperature
- Cholesterol levels
- Age
Continuous data allows precise measurement and statistical analysis.
Give an example of Discrete Data.
- Number of hospital visits
- Number of medications taken
- Number of lymph nodes involved
This data consists of whole numbers without fractions.
Which type of data is represented by whole numbers without fractions
e.g. The number of lymph nodes affected by cancer
Discrete Data
vs continuous (with fractions)
Data that represent categories without any intrinsic order or ranking
Examples include blood type (A, B, AB, O) and gender (male, female).
Nominal Data
By name
Give an example of Nominal Data.
These are labels or names without order.
- Blood type
- Gender
- Presence/absence of a symptom
Data with a meaningful order or ranking, but intervals between ranks are not necessarily equal/clarified
Examples include pain severity and cancer stages.
Ordinal Data
Provide an example of Ordinal Data
The categories have a clear order, but not necessarily numerical
- Pain severity (mild, moderate, severe)
- Cancer stages (Stage I, II, III, IV)
- Patient satisfaction ratings (good-poor)
Vs nominal - only named types without an order, or categorical - named and by order
Both nominal data and ordinal data are examples of ______________data.
Categorical Data.
A type of numerical data that can take any value within a range and have meaningful intervals
Examples include blood pressure and temperature.
Continuous Data
A type of numerical data that take specific, separate values that has no fractions.
Examples include the number of hospital visits and medications taken.
Discrete Data
Define Student’s T-test.
A statistical test used to compare the means of two groups.
Indications to use the:
1) Unpaired student t-test
2) Paired student T-test
1) Unpaired (Independent) t-test: Used when comparing means from two independent groups, e.g. blood pressure in patients receiving drug A versus drug B.
2) Paired t-test: Used for related or matched participants, e.g. pre- and post-treatment measurements in the same patients.
True or false: The Chi-square test assesses relationships between categorical variables.
TRUE
It evaluates how likely it is that an observed distribution is due to chance.
Fill in the blank: The null hypothesis states there is ______ difference between groups.
no significant
