## INTRODUCTION

Test Taking Tips

• Memorize the following table for easy calculation of sensitivity, specificity, and positive and negative predictive values.

• Know the differences between different types of statistical tests.

• Not a lot changes in statistics, so similar questions are phrased differently annually. ### What is sensitivity?

• The proportion of truly diseased persons in a screened population who are identified as being diseased by the test. It is a measure of the probability of correctly diagnosing a condition.

### What is the sensitivity equation?

• True positive / (true positive + false negative)

### What is specificity?

• The proportion of truly nondiseased persons who are so identified by the screening test

### What is the specificity equation?

• True negative / (false positive + true negative)

### What is the false-positive rate?

• 1 – specificity

### What is the false-negative rate?

• 1 – sensitivity

### What is the positive predictive value?

• The probability that a person with a positive test result has the disease

### What is the positive predictive equation?

• True positive / (true positive + false positive)

### What is the negative predictive value?

• The probability that a patient with a negative test result really is free of the disease

### What is the negative predictive value equation?

• True negative / (false negative + true negative)

### What is the definition of prevalence?

• The total number of cases of a given disease in a specified population at a designated time

### What is the definition of incidence?

• The number of new cases of a given disease during a given period in a specified population

### What is the absolute risk reduction?

• The absolute arithmetic difference in outcome rates between control and experimental patients in a trial

### What is the relative risk reduction?

• The proportional reduction in outcome rates between control and experimental patients in a trial

### A range of values that has a specified probability of containing the rate or trend is called what?

• Confidence interval

### A method of studying a drug or procedure in which both the subjects and investigators are kept unaware of who is actually getting which specific treatment is called what?

• Double-blind method

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