©SOPHIABENNET@2024/2025 Tuesday, August 20, 2024 10:21 AM
USMLE Step 1 Biostatistics/Epidemiology Exam
Study Guide with Complete Solutions
Sensitivity - Answer✔️✔️-TP / (TP + FN)
Specificity - Answer✔️✔️-TN / (TN + TP)
Positive Predictive Value - Answer✔️✔️-TP / (TP + FP)
Negative Predictive Value - Answer✔️✔️-TN / (FN + TN)
Incidence Rate - Answer✔️✔️-# of new cases in a certain time period /
population that is at risk during that time period
This looks at new incidences occurring during a time period
Prevalence - Answer✔️✔️-# of existing cases / population at risk
Looks at ALL current cases
Odds Ratio - Answer✔️✔️-(a/c) / (b/d) OR ad / bc
Relative Risk - Answer✔️✔️-[a / (a + b)] / [c / (c + d)]
Attributable Risk - Answer✔️✔️-(a / (a+b) ) - (c / (c+d) )
Gaussian curve standard deviation %'s - Answer✔️✔️-+/- 1 SD = 68%
+/- 2 SD = 95%
1
, ©SOPHIABENNET@2024/2025 Tuesday, August 20, 2024 10:21 AM
+/- 3 SD = 99.7%
Type 1 error (alpha) - Answer✔️✔️-you sAw a difference that did not really
exist
(convicting an innocent man)
Type 2 error (beta) - Answer✔️✔️-you were Blind to a difference that did
exist
(setting a guilty man free)
Power - Answer✔️✔️-1-beta or in other words, 1 - type 2 error
(increasing sample size will increase power, there is POWER in numbers.
Also, increasing Precision will increase power)
SEM - Answer✔️✔️-SD / square root of n
Confidence Interval - Answer✔️✔️-range from [mean - Z (SEM)] to [mean +
Z (SEM)]
Z = 1.96 for 95% CI
Z = 2.58 for 99% CI
On the test, it may be easier to remember the Z values as 2 and 2.5 for
easier calculations and memorization
t - test - Answer✔️✔️-checks difference between the means of 2 groups
2
USMLE Step 1 Biostatistics/Epidemiology Exam
Study Guide with Complete Solutions
Sensitivity - Answer✔️✔️-TP / (TP + FN)
Specificity - Answer✔️✔️-TN / (TN + TP)
Positive Predictive Value - Answer✔️✔️-TP / (TP + FP)
Negative Predictive Value - Answer✔️✔️-TN / (FN + TN)
Incidence Rate - Answer✔️✔️-# of new cases in a certain time period /
population that is at risk during that time period
This looks at new incidences occurring during a time period
Prevalence - Answer✔️✔️-# of existing cases / population at risk
Looks at ALL current cases
Odds Ratio - Answer✔️✔️-(a/c) / (b/d) OR ad / bc
Relative Risk - Answer✔️✔️-[a / (a + b)] / [c / (c + d)]
Attributable Risk - Answer✔️✔️-(a / (a+b) ) - (c / (c+d) )
Gaussian curve standard deviation %'s - Answer✔️✔️-+/- 1 SD = 68%
+/- 2 SD = 95%
1
, ©SOPHIABENNET@2024/2025 Tuesday, August 20, 2024 10:21 AM
+/- 3 SD = 99.7%
Type 1 error (alpha) - Answer✔️✔️-you sAw a difference that did not really
exist
(convicting an innocent man)
Type 2 error (beta) - Answer✔️✔️-you were Blind to a difference that did
exist
(setting a guilty man free)
Power - Answer✔️✔️-1-beta or in other words, 1 - type 2 error
(increasing sample size will increase power, there is POWER in numbers.
Also, increasing Precision will increase power)
SEM - Answer✔️✔️-SD / square root of n
Confidence Interval - Answer✔️✔️-range from [mean - Z (SEM)] to [mean +
Z (SEM)]
Z = 1.96 for 95% CI
Z = 2.58 for 99% CI
On the test, it may be easier to remember the Z values as 2 and 2.5 for
easier calculations and memorization
t - test - Answer✔️✔️-checks difference between the means of 2 groups
2
