Stats

ALS 434 Lecture 1: Preliminary

Fall 2014

Introduction to Biostatistics

Descriptive statistics – summarize and describe the data Inferential statistics – how to reach conclusions that extend beyond the immediate data alone; to make inferences from our data to more general conditions Variable – a characteristic that can vary (e.g. height, blood pressure, gender, race/ethnicity, etc.)  Quantitative variable – consist of numbers representing counts or measurements. A variable that can be measured or counted. o Discrete variable – the number of possible values is either a finite number or a “countable” number. (e.g. number of patients, length of hospital stay in days) o Continuous variable – there are an infinite number of possible values between any two specific values such that there would be no gaps. (e.g. height, blood pressure)  Qualitative (categorical) variable – can be separated into different categories that are distinguished by some nonnumeric characteristics. (e.g. gender, race)

Example 1 (qualitative or quantitative variable?): From a sample of students in your statistics class, you collect the following: the student’s name, gender, SAT score, age, and their grade in a freshman level math class. Which variables are qualitative or quantitative? 1. The variable student’s name is 2. The variable student’s gender is 3. The variable student’s SAT score is 4. The variable student’s age is 5. The variable student’s grade in a freshman level mass class is

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ALS 434 Lecture 1: Preliminary Measurement scales (levels of measurements)

Fall 2014

When we observe and record a variable, it has characteristics that influence the type of statistical analysis that we can perform on it. These characteristics are referred to as the level of measurement of the variable. The first step in any statistical analysis is to determine the level of measurement; it tells us what statistical tests can and cannot be performed. There are four levels or scales of...