319 - Chapter 1

Population

The entire collection of objects or outcomes about which information is sought.

Sample

A subset of a population containing the objects or outcomes that are actually observed.

Simple Random Sample

A sample chosen by a method where each collection of n population items is equally likely to make up the sample.

Sample of Convenience

A sample obtained in a convenient way, not drawn by a well-defined random method.

Tangible Populations

Populations consisting of physical objects, which are always finite.

Conceptual Population

A population that consists of all the values that might possibly have been observed under identical experimental conditions.

Independent Items

Items in a sample are independent if knowing the values of some does not help predict the values of others.

Finite Population Independence

Items may be treated as independent if the sample contains 5% or less of the population.

Sampling with Replacement

A method where the population remains the same on every draw, making sampled items truly independent.

Standard Deviation

A quantity that measures the degree of spread in a sample, indicating variation in the data.

Median

The middle number in a sample when values are ordered from smallest to largest; for even sample sizes, it is the average of the two middle numbers.

p% Trimmed Mean

The number of data points to be trimmed is np/100; round to the nearest whole number if not whole.

Quantitative Variables

Variables that take numerical values.

Qualitative Variables

Variables that take categorical values, classifying each item under a category.

Controlled Experiment

An experiment where the experimenter controls the values of the factors.

Observational Study

A study where the experimenter observes factors without controlling them.

Statistic

A number that reveals a characteristic of a sample; numerical summaries of a sample.

Parameter

Numerical summaries of a population.

Sample Mean

Indicates the center of the data.

Quartiles

Values that divide the data into quarters.

First Quartile (Q1)

The median of the lower half of the data, computed as 0.25(n+1).

Third Quartile (Q3)

The median of the upper half of the data, computed as 0.75(n+1).

Median (Q2)

The second quartile.

pth Percentile

Divides the sample so that p% of the sample values are less than it, and (100-p)% are greater.

Frequency

The number of sample items that fall into a given category.

Sample Proportion

The frequency divided by the sample size; also known as relative frequency.

Number of Classes

Calculated as sqrt(n).

Class Frequency

The number of sample values in a class interval.

Relative Frequency

Frequency/sample size; the proportion of sample values in a class interval.

Density

Relative frequency/class width.

Class Width

(Upper limit of the class - Lower limit of the class) / sqrt(n).

Unimodal Histogram

A histogram with only one peak.

Bimodal Histogram

A histogram with two peaks, often indicating subsamples.

Lower Outlier Boundary

Q1 - 1.5*IQR.

Upper Outlier Boundary

Q3 + 1.5*IQR.

Bivariate Data

Data consisting of pairs of values.