## Ultra HighYield Review

Most USMLE Step 1 candidates probably spend no more than 3 to 5 hours reviewing biostatistics. In this short time, the candidate should be able to memorize the ultra-high-yield items in this checklist. Together with a background understanding from the previous chapters in this book, these items should equip the candidate to pick up a good number of points in a subject area that is neglected by many students and medical schools, which should mean that biostatistics in itself will be relatively a high-yield subject on the examination for the candidate. After this list and the referenced material in this book have been reviewed, a self-test can be administered by using the USMLE-style exercise questions at the end of each chapter.

The USMLE Step 1 candidate should:

□ be able to use the addition and multiplication rules of probability (page 3).

□ be able to find and use the three measures of central tendency (page 11).

□ understand the standard deviation (page 13).

□ know and be able to use the proportions of the normal distribution which are within or beyond 1, 2, or 3 standard deviations from the mean (page 13).

□ understand and be able to use ^-scores (page 15).

□ understand confidence limits and be able to find 95% confidence limits (page 25). C understand precision and accuracy (the dartboard analogy) (page 26).

□ understand how sample size relates to precision (page 26).

□ know exactly how to increase precision and reduce the width of the confidcncc interval (page 26).

□ know how to be 95% confident about the true mean of a population (page 26).

□ know the meaning and limitations of p values and statistical significance (page 37).

□ know the meaning of type I and type II errors in hypothesis testing and in diagnostic testing (page 37).

□ know how to avoid type I and type II errors in hypothesis testing (page 37).

□ know the meaning of a test's power, how to increase it, and the dangers of a lack of power (the radar screen analogy) (pages 37-38).

□ know the meaning of main and interaction effects in ANOVA (the beards and lipstick analogy) (page 44).

□ know the meaning and use of correlation coefficients and r values (page 50).

□ be able to avoid the temptation to infer causation from correlation (page 52).

□ be able to interpret scattergrams of bivariate distributions (page 51).

□ calculate and know the meaning of the coefficient of determination (r2) (page 52).

□ know what regression techniques do (pages 52-53).

□ memorize Table 4-1 to be able to choose the appropriate basic test for a given research question (page 54).

□ know the purposes of the features of clinical trials: (pages 59-60)

□ randomization or matching.

□ cohort studies (the Framingham study and chimney sweeps example) (pages 62-63).

□ case-control studies (DES and vaginal carcinoma study) (page 63).

□ be able to choose the appropriate type of research study for a given question (pages

□ know the meanings of and be able to find: (pages 68-69)

□ and the relationships between them (the epidemiologist's bathtub) (page

□ know the meaning of case-fatality and attack rates (page 70).

□ know the meanings of and be able to find: (pages 72-73)

□ relative risk and relative risk reduction.

□ number needed to treat.

□ know the meaning of validity (including internal and external validity) and reliability (page 78-79).

□ know the meanings of and be able to find:

□ positive predictive value (page 83).

□ negative predictive value (page 83).

□ know how changing a test's cutoff point will affect its sensitivity and specificity (page 82).

□ know what kind of test to use to rule in or rule out a disease (mnemonics "Snout" and "Spin") (page 81).

## Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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