Variables and Data Management - Lecture

Categorical variables group things, they don’t make measurements. Categorical variables may be attributes, which have no rank. Sometimes called nominal.

• Binary nominal variable - only two categories

Categorical variables that have a ranking, as ranked or ordinal.

Categorical variables are also known as qualitative

Quantitative variables are numerical and have a value that can be measured.

Discrete - expressed as integers, typically

Continuous quantitative variables can assume any value within a given range.

Transformed variable - a variable which we have performed some sort of mathematical operation. Logarithmic is the most common.

Derived variable - a variable that is produced by using a mathematical operation on two variables to calculate a third variable. Rate is a common one.

Rounding Rules

Intermediate Results - never round off; only round off at the very end

Precision of measurement - the number of digits displayed for a continuous measurement indicates the precision with which it was measured

Significant figures in a final answer - Precision of the final answer represents the precision of the original measurements.

Rounding to three significant figures:

• Always round down if the last value is less than 5

• Always round up if last value is more or equal to 5

• If last number is 5:

  • Round up is if the previous number is five

  • Round down if the previous number if even

Calculations from exact values are not rounded

Independent and Dependent Variables

Dependent variable is when you trying to see how it is impacted.

Independent variable is labeled as x, and the dependent variable is expressed as y