Lecture 36 - Biostats - Intro to Probability

Lecture 36 - Biostats - Intro to Probability - Characterize...

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Characterize scales of measurement (nominal, ordinal, continuous) Interpret frequency distribution in describing a set of biological measurements Define mean, median, mode, percentile, variance, standard deviation, range, and inter-quartile range and describe how they are used Distinguish between the standard deviation and the standard error and explain the appropriate use of each Contrast the features of a normal distribution with those of a skewed distribution Distinguish when to use nonparametric vs. parametric statistics Explain what is meant by probability - Scales of measurement o Nominal, ordinal, interval, ratio scales o Interval and ratio also called numerical or continuous o Possible properties of a scale: Identity: each number has an inherent meaning Magnitude: inherent order from small to large Equal intervals: differences between units on the scale is the same, i.e. 1 to 2 is same as 101 to 102 Absolute/true zero: Zero represents absence - Nominal Scales o A nominal scale is used where arbitrary numbers or designations can be given to categories of the data o Examples are gender, ethnic groups, disease state (i.e. hypertension, yes or no) o No ordering is implied, i.e. 1=female, 2=male is same as 1=male, 2=female; male is not > female o No quantitative information, qualitative in nature o Identity property is only one that applies - Ordinal Scales o A scale that incorporates inherent order in the data o Properties include magnitude and identity, but NOT equal distances or true zero o Examples include: Cancer stages, i.e. lung cancer, stage I is confined to the lung, stages II and III are confined to the chest, and IV is metastasis Apgar scores, scale 0-10 Ranked preferences, i.e. soda or coffee Levels of agreement, i.e. Likert scale - Interval Scale o A scale in which a given distance along the scale means the same regardless of where on the scale o Properties include identity, magnitude, and equal distance, but NOT true zero point o Differences make sense, but ratios do not Examples include: Temperature, Celsius or Farenheit Dates Test scores, i.e. SAT or GRE scores - Ratio Scale o Sa m e a s a n interval scale, but zero has m e a ning, n a m ely the abs enc e of a characteristic o So properties include: identity, m a gnitude, equ al o It m akes s ens e to s ay 2 m is twice a s large as 1 m o Examples include: Height, weight, length Money Biomarkers, i.e. c-reactive protein, cholesterol, Sum m arizing Data - What is a frequ ency distribution? o
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Lecture 36 - Biostats - Intro to Probability - Characterize...

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