Biostadistics

Question 1

Intention to treat analysis

Answer 1

subject results are analyzed according to the group that they were initially assigned to (not according to adherence) is one technique used to analyze outcome data and preserve randomization

Question 2

When the cut-off point of a test is decreased, what happen with specificity and sensitivity?

Answer 2

Decrease in specificity (TN/(TN+FP)) and an increase in sensitivity (TP/(TP+FN)).
To identify more patients (usually in the form of decreasing the cutoff value) but with more false positives occurring.

Question 3

p-value of 0.052 meaning in a study that compares two medications?

Answer 3

There is a 5.2% chance that A is more effective than B is due to chance.

Question 4

If the cutoff value of a diagnostic test is increased (meaning it takes more of a finding to suggest a diagnosis), what should we say about specificity and sensitivity?

Answer 4

The sensitivity decreases while the specificity increases.

Question 5

If the confidence interval of a relative risk contains the value 1

Answer 5

The result is likely not epidemiology significant.

Question 6

Berkson bias

Answer 6

occurs when hospitalized study subjects are more likely to have a greater burden of illness than other possible subjects.

Question 7

Attrition bias

Answer 7

Occurs because patients who are lost to follow-up may be different from those who remain in the study.

Question 8

Selection bias

Answer 8

A sampled population is not representative of the population researchers are trying to study.
Due to inappropriate recruitment or attrition of study participants. E
- non-response bias (participants who answer a survey may be less sick than participants who don’t)
- the healthy worker effect (employed subjects may be healthier than others)
- volunteer bias (volunteers may be different from those who do not volunteer)
- late-look bias (patients with severe disease may be less likely to be studied due to death or disability)
-Attrition bias (patients who are lost to follow-up may be different from those who remain in the study).

Question 9

Response bias

Answer 9

Occurs when the outcome metric is a subjective patient-reported measure because patients may change their responses in a non-random manner.

Question 10

The factors that increase prevalence

Answer 10

Increase in new cases (increased incidence)
An improvement in the quality of care (prolonged duration of disease)
Improved diagnostic ability (early detection thus more cases).

Question 11

Normal distribution, mean, median and mode.

Answer 11

In a normal distribution, the mean, median, and mode are identical