Descriptive Statistics

25 terms · Vocabulary

Population

A collection of individuals about which we want to draw conclusions

Census

Collection of information from the whole population

Sample

A subset of the population- it's important to choose a sample at random to avoid bias in the results

Survey

Collection of information from a sample

Data

Information about individuals in a population

Parameter

A numerical quantity measuring some aspect of the population

Statistic

A quantity calculated from data gathered from a sample- usually used to estimate a population parameter

Distribution

The pattern of variation of data. The distribution may be described as symmetrical, positively skewed, or negatively skewed

Outliers

Data values that are either much larger or much smaller than the general body of data- they should be included in an analysis unless they are the result of human or other error

Designed experiment

A method of experimentation in which you can control as many variables as possible in order to isolate the effects of a response variable

Observational study

A method of data collection in which the objects of study are observed in their natural settings and the variables are recorded

Survey

A method of data collection where the researcher selects a sample from the population and measures the variable of interest

Simple random sample

A method in which each combination of people has an equal chance of being selected- the sample is representative of the population and is independent

Exploratory data analysis

Using graphs and numerical summaries to describe variables in a data set and their relationship

Dot plots

Can be used to get an initial graphical view of data

Stem and leaf plots

An efficient method of graphing information using actual amounts: clusters, gaps, outliers are clearly identified.

Frequency histogram

Type of bar graph that shows frequency distributions

Relative frequency histogram

Has the same shape and horizontal scale as a histogram, but the vertical scale is marked with relative frequencies instead of actual frequencies

Discrete numerical data

The variable value can be represented as isolated points on a number line

Systematic sampling

A method in which you randomly choose one number from "l" to "k" and continue to select the kth element

Strata sampling

To divide the population into 2 or more non-overlapping subsets called strata

Cluster sampling

Population is organized into groups (i.e, neighborhoods/departments), and sampling unit is selected by a simple random sample

Convenience sampling

create a sample by using data from population members that are readily available

Self-selected sample

members of the population select themselves by volunteering

Bias

A flaw in the sampling procedure that makes it more likely that the sample will NOT be representative of population