Lecture 8 Flashcards
Common sources of measurement error
– Systematic error
– Random error
– Errors in alternate forms of measurement
The act or process of assigning numbers or values to phenomena according to a rule.
• The dimension, quantity, or capacity determined by measuring
What is measurement?
All measurements can be reduced to just two
components:
number and unit
There are two kinds of measurement errors:
system errors and random errors
Measurement errors occur when:
the collected data do not accurately portray the concept that we intend to measure
When we deal with data from different sources and countries we need to standardize these data into
standardized comparable units. What are some examples of units of measure that need to be standardized:
Examples of this issue are currencies used in different countries, weight (kg vs lb), length (meter vs foot)
If a loud construction is going on just outside of a classroom where pupils are writing a test, this noise is liable to affect all of the children‘s scores. What is this an example of?
Systematic Error. Often called biases in the
measurements. A systematic error occurs when the collected information consistently reflects an inaccurate picture of the concept that we are
attempting to measure
We may ask questions in a way that predisposes
individuals to answer in the way we want them to. For example, “It is better to give than to receive?” This is called the:
acquiescent response set.
Individuals may be biased to answer the questions in the ways that distort their true views or behaviors. This bias can be minimized by anonymity:
What is social desirability bias
In a particular testing, some children may be in a good mood and others may be depressed. What is this a (terrible) example of?
Random error. The key point about random errors is that they do not have any consistent effects across the entire sample; they do not affect the average only the variability around the average.
The steps you can take to minimize errors depend mainly on the:
data collection methods. For example, unbiased wording, pretesting, consistency among testers to reduce interrater bias, unobtrusive observation, use different methods to collect the same information (triangulation)
This concerns the amount of random error in a measure and measurement consistency and the chance that a given measurement procedure will yield the same results of a given phenomenon at another time. In another word: repeatability
What is reliability
Inter-observer or inter-rater reliability
The degree to which different observers/raters generate consistent estimates of the same phenomenon
Test-retest reliability
The consistency of a measure over time
Internal consistency reliability
he consistency of results across items within a test,
e.g. the split-halves method
