Standard Error (SE)

Definition
A measure of the variability of an estimate due to sampling
Depends on variability in the population and sample size
Foundational measure

Margin of Error (MOE)
Definition

A measure of the precision of an estimate at a given level of confidence (90%, 95%, 99%)
Confidence level of a MOE
MOEs at the 90% confidence level for all published ACS estimates
Margin of Error (MOE)

Confidence Interval
Definition

A range that is expected to contain the population value of the characteristic with a known probability.
Formula

Where
LCL is the lower bound at the desired confidence level
UCL is the upper bound at the desired confidence level
is the ACS estimate and
is the margin of error at the desired confidence level
Confidence Interval computation


Coefficient of Variation (CV)
Definition
The relative amount of sampling error associated with a sample estimate
Sampling Error is related to Sample Size.
.The larger the sample size, the smaller the uncertainty or sampling error
•Combining ACS data from multiple years increases sample size and reduces sampling error
•All sample surveys have sampling error – including decennial census long-form data

How to Use Measures Associated With Sampling Error
How are Measures of Sampling Error Used?
•To indicate the statistical reliability and usability of estimates
•To make comparisons between estimates
•To conduct tests of statistical significance
•To help users draw appropriate conclusions about data

Test of Statistical Significance
Definition


A test to determine if it is unlikely that something has occurred by chance
A “statistically significant difference” means there is statistical evidence that there is a difference