Biostats Flashcards

1
Q

Relative risk equation?

A

RR = risk of an outcome in an exposed group/ risk of the same outcome in an non exposed group

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2
Q

What is a cross sectional analysis and what is it used for?

A

Data gathers at one point in time
Can determine prevalence of an outcome in a population
Identify specific risk factors and help generate hypothesis for further research

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3
Q

False negative equation?

A

FN = 1- sensitivity x number of pts who truly have the disease

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4
Q

True positive equation?

A

TP= Sensitivity x number of patients who truly have the disease

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5
Q

Meta analysis

A

Groups results of several trials to increase statistical power and provide overall pooled effect estimates

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6
Q

How to determine if CI is statistically significant

A

For odds ratio and relative risk the null value is 1 ( as long as CIS do not cross the null value it is statistically significant)

For difference the null value is 0

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7
Q

Two sample test

A

Statistical method to compare the means of 2 groups of subjects

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8
Q

P value in a study with a large number of pts

A

A smaller p value is used to decrease the risk of of false positive results

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9
Q

Precision of test

A

Precision ( reliability) is the ability of the test to reproduce identical results with repeated measurements

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10
Q

Health promotion

A

Is an e.g of 1o prevention
Enabling people to control their health and determinants

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11
Q

Observer bias

A

Occurs with the investigator’s evaluation is affected by preconceived expectations or prior knowledge leading to overestimation

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12
Q

Independent event probability

A

If you have multiple independent events you multiply the probability

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13
Q

Prospective cohort study

A

Patients are selected on their exposure status and followed up over time for development of disease

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14
Q

Risk equation

A

Risk of developing the disease with exposure/ all subjects who were exposed

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15
Q

Main purpose of blinding in a study is to prevent

A

Observer bias by either pt or researcher

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16
Q

Area under the curve

A

The more accurate a test is ( high sensitivity and specificity) the closer AUC value is to 1

17
Q

The average of a dataset of values

A

Equivalent to mean
Total number of episodes/total number of pts

18
Q

Allergic contact dermatitis features

A

Type IV hypersensitivity reaction
Intercellular epidermal oedema, with infiltration of lymphocytes and eosinophils

19
Q

Reducing significance set alpha in a study will lead to

A

Any significant findings will be reported with greater confidence

Decreased significance level = increased confidence level

20
Q

Cross sectional study

A

Exposure and outcome measured simultaneously at a particular point in time
Prevalence study

21
Q

Positively skewed curve relationship between mean, median and mode

A

Mode is closer to the middle and mean closer to tail ( RT tail)
Median in the middle
Mode <median < mean

22
Q

Attack rate equation

A

Number of people who contact an illness/ number of people who are at risk of contracting that illness

23
Q

Prevalence can be increased by

A

Incidence or prolonged disease duration

Prevalence = incidence x disease duration

24
Q

Normal distribution mean and median

A

In a normal distribution curve mean and median are equal therefore 50% of observations will lie below the mean and 50% above

25
Lead time bias
When a test diagnoses a condition earlier than conventional causing an apparent increase in survival time but no improvement on actual time to mortality
26
Negative predictive value
Probability that an individual doesn’t have the disease given a negative result NPV= TN/ TN+FN
27
Misclassification bias
Incorrect categorization of subject re: their outcome status or both
28
Hawthorne effect
Tendency of the study subjects to change their behaviour as a result of awareness that they are being studied
29
Greatest preventive intervention in almost all patients
Smoking cessation
30
T test ( paired t test )
Compares the mean of 2 groups Quantitative test
31
Precision and accuracy
High precision it consistently provides same or similar value High accuracy test provides measurements see or similar to actual value
32
Absolute risk reduction
Event rate in control group - event rate in the treatment group Event rate in treatment= # of event in treatment arm / # of subjects
33
Absolute risk increase
Difference in the rate (risk ) of the adverse event between treatment and control group ARI= Rate AE treatment - Rate AE control
34
Number needed to harm
NNH= 1/ ARI