Descriptive Statistics

Population

All individuals or measurements of interests

Sample

Subset used to make inferences (conclusions with reasoning) about a population.

Parameter

Measurement of the population.

A numerical value that describes a population characteristic.

Statistic

Measurement of the sample.

A numerical value computed from the sample data to estimate a parameter

Descriptive Statistics

• Methods used to summarize or describe the data

• Mean

• Median

• Range

• Variance

• Standard

• Deviation

Inferential Statistics

Methods for making predictions or generalizations about a population from a sample.

Quantitative data

Numerical data that can be measured (Voltage, pressure, and time)

Qualitative data

Categorical data that describe attributes (Color, type, and label)

Mean (x̄)

Average value

x̄ = (Σx)/n

Mathematical representation of Mean

Median

• The middle value when data are arranged in order

• Divides the data into two equal halves

Mode

The most frequently occurring data value.

Range

The difference between the largest and smallest observation.

Variance

Measure of data spread around the mean.

s^2 = (Σ(x - x̄)^2)/(n - 1)

Mathematical representation of variance.

Standard deviation

• Square root of variance

• Describes the average distance from the mean.