Chapter 2: Organizing, Displaying, and Describing Data

Vocabulary practice flashcards covering Chapter 2: Organizing, Displaying, and Describing Data from Statistical Methods for Health Care Research. Includes definitions of measurement scales, data display techniques, central tendency, dispersion, and distribution shapes.

Variable

Any characteristic that can and does assume different values for different people, objects, or events being studied.

Nominal Scale

A measurement scale where numbers are arbitrarily assigned simply as codes to represent categories, with no meaningful numerical order (e.g., gender, ethnicity).

Ordinal Scale

A measurement scale where numbers represent categories placed in a meaningful order (e.g., from lowest to highest), but intervals between values are unknown or unequal, and there is no true zero (e.g., pain scale, military rank).

Interval Scale

A measurement scale where numbers have equal intervals between them and allow addition and subtraction, but lack a true zero, preventing the calculation of ratios (e.g., Fahrenheit temperature, SAT, GRE, MCAT).

Ratio Scale

A measurement scale where numbers have equal intervals and an absolute "true" zero determined by nature, representing the absence of the phenomenon (e.g., weight, pulse rate, age, cholesterol level).

Central Tendency

A statistical characteristic describing the most frequently occurring or typical values in a distribution.

Dispersion

A statistical property describing how the values in a data set are spread out.

Outlier

An unusual value that does not fit the general pattern of the data set.

Frequency Distribution Table

A tabular visual display of data that presents the possible values of a variable, raw frequencies, relative frequencies, and cumulative frequencies.

Raw Frequency

The exact number of cases or observations possessing a particular value or falling into a specific interval.

Relative Frequency

The percentage of the total sample represented by cases with a specific value.

Cumulative Frequency

The total percentage of cases having values up to and including a given value of the variable.

Histogram

A visual display for data that are at least ordinal in scale, where the variable values are plotted on the x-axis using mutually exclusive, exhaustive, and even-width class intervals with touching bars.

Mode

The most frequently recurring value in a data set, which can be unimodal or multimodal, and is appropriate for nominal, ordinal, interval, and ratio level data.

Median

The value in the middle of a distribution representing the $50^{\text{th}}$ percentile, appropriate for ordinal, interval, and ratio level data.

Mean

The arithmetic average of a distribution calculated by dividing the sum of all values by the total number of values ($\bar{x} = \frac{\sum x_i}{n}$), most appropriate for interval and ratio data.

Range

The difference between the highest and lowest values in a data set, appropriate for ordinal, interval, and ratio level data.

Variance ($S^2$)

The sum of the squared deviations of each value from the mean, divided by $n - 1$: $S^2 = \frac{\sum (x_i - \bar{x})^2}{n - 1}$.

Standard Deviation ($s$)

The average distance of each data point from the mean, calculated as the square root of the variance ($s = \sqrt{S^2}$); most appropriate for interval and ratio data.

Symmetrical Distribution

A distribution in which data are evenly distributed about the center, having an equal amount of data on the left and right sides (not all symmetrical distributions are normal).

Skewed Distribution

A distribution where data values are not evenly distributed about the center, resulting in asymmetry categorized as right-skewed or left-skewed.

Positive Skew (Right-skew)

An asymmetrical distribution whose tail extends toward the higher, positive values on the right side.

Negative Skew (Left-skew)

An asymmetrical distribution whose tail extends toward the lower values on the left side.