QuestionSBA
QuestionChoice
Studies with positive or statistically significant results are more likely to be published in journals, whereas those without statistically significant results are less likely to be published. This may make effect sizes appear better or greater than they actually are. This is not the type of bias represented in this question.
53341
e
Publication bias
QuestionChoice
This is incorrect because time interval bias occurs when a clinical trial is stopped early once the desired conclusion is achieved.
53339
c
Time interval bias
QuestionChoice
Recall bias refers to a skew that occurs due to individuals with a certain outcome (or without a certain outcome) being more (or less) likely to recall an exposure, as the outcome has already been achieved. For example, individuals with lung cancer may be more likely to recall even small amounts of smoking history, which may positively skew the data.
53340
d
Recall bias
QuestionChoice
Sampling bias describes a skew in the data that occurs when some members of a population are more likely to be selected for inclusion within a study than others. There is no indication of this being an issue within the question, for example an inadequate mix of genders or ethnicities.
53338
b
Sampling bias
QuestionChoice
Bias refers to a skew in the data due to a systematic issue at any stage of a study. In this case, participants have dropped out due to unwanted side-effects, which is likely to give a negative skew to the results, as they are not followed up for long enough or included in the final results, to determine if the drug had an impact on their blood pressure or not. This is referred to as attrition bias.
53337
a
Attrition bias
Concept
Chapter
# Definition

Selection bias is the selection of individuals, groups or data for analysis in such a way that proper randomization is not achieved, thereby ensuring that the sample obtained is not representative of the population intended to be analysed.

# Types of Selection Bias 

Some of the different types of Selection Bias are:

# Sampling bias

This is due to a non-random sample of a population, causing some members of the population to be less likely to be included than others, resulting in a biased sample, defined as a statistical sample of a population (or non-human factors) in which all participants are not equally balanced or objectively represented

# Time interval bias

Early termination of a trial at a time when its results support a desired conclusion

# Susceptibility bias

When one disease predisposes for a second disease, and the treatment for the first disease erroneously appears to predispose to the second disease. Partitioning data with knowledge of the contents of the partitions, and then analysing them with tests designed for blindly chosen partitions. Selection of which studies to include in a meta-analysis.

# Attrition bias

Is a kind of selection bias caused by attrition or loss of participants, discounting trial subjects/tests that did not run to completion.

# Intention to treat analysis

Intention to treat analyses are done to avoid the effects of crossover and dropout, which may break the random assignment to the treatment groups in a study
593
607
Selection Bias
Topic
51
Medical Statistics
10728
Attrition bias occurs when participants drop out of a study or trial in a way that affects the validity of the results, leading to a biased sample that may not accurately represent the original population.
A clinical trial recruited 1000 participants to evaluate the efficacy of a new anti-hypertensive. 500 participants were randomly assigned to receive amlodipine whilst the other 500 participants were assigned to receive a new anti-hypertensive for 1 year. The primary objective of the study was to evaluate the efficacy of each drug in reducing blood pressure in both groups. However, 21 participants taking amlodipine and 57 participants taking the new anti-hypertensive left the clinical trial before it completed as they experienced unwanted side effects. The study did not include these participants in the final results and concluded that the new anti-hypertensive was not effective at reducing blood pressure compared to amlodipine.

Which of the following types of bias is this study at risk of?
a