A test is reliable to the extent that whatever it measures, it measures it consistently. If I were to stand over a size and the range read 15 pounds, I would wonder. Imagine I were to step off the size and stand on it again, and again it read 15 pounds. The level is producing constant results. From a research point of view, the scale seems to be reliable because whatever it is calculating, it is calculating it regularly. Whether those constant results are valid is another question. However, a musical instrument cannot be valid if it's not reliable.
The real difference between consistency and validity is mostly a matter of meaning. Reliability estimates the persistence of your way of measuring, or more basically the degree to which a musical instrument measures the same manner each time it is utilized within the same conditions with the same topics. Validity, on the other hands, involves the amount to which your are calculating what you are supposed to, more simply, the precision of your way of measuring. It is my notion that validity is more important than trustworthiness because if an instrument does not accurately assess what it is meant to, there is absolutely no reason to utilize it even if it measures constantly (reliably).
There are three major types of reliability for some musical instruments: test-retest, equivalent form, and inner consistency. Each procedures consistency a bit differently and a given instrument do not need to meet up with the requirements of every. Test-retest measures steadiness from one time to the next. Equivalent-form measures consistency between two variations of a musical instrument. Internal-consistency measures persistence within the tool (consistency on the list of questions). A fourth category (scorer contract) is often used with performance and product assessments. Scorer agreement is reliability of rating a performance or product among different judges who are rating the performance or product. In most cases, the longer a test is, a lot more reliable it is commonly (up to point). For research purposes, a minimum reliability of. 70 is necessary. Some researchers feel that it should be higher. A dependability of 0. 70 indicates 70% reliability in the ratings that are made by the tool. Many lab tests, such as accomplishment tests, strive for 0. 90 or more reliabilities.
Relationship of Test Forms and Testing Sessions Required for Trustworthiness Procedures
Testing Trainings Required
Test Forms Required
Equivalent (Different) Form
1 Test-Retest Method. A similar instrument is given twice to the same group. The trustworthiness is the correlation between the results on the two instruments. If the results are reliable over time, the scores should be similar. The secret with test-retest dependability is determining how much time to wait between your two administrations. One should wait around long enough therefore the subjects don't remember how they responded the very first time they completed the device, but not such a long time that their understanding of the materials being measured has changed. This may be a couple weeks to a couple months.
2 Equivalent-Form (Parallel or Alternate-Form) Method. Two different editions of the tool are manufactured. We presume both measure the same thing. The same things complete both instruments through the same time frame. The scores on the two devices are correlated to assess the consistency between your two types of the tool.
3 Internal-Consistency Method. Several internal-consistency methods are present. They have one thing in common. The content complete one tool one time. For this reason, this is actually the most basic form of reliability to investigate. This method measures regularity within the tool three various ways.
- Split-Half. A total report for the peculiar amount questions is correlated with a total report for the even number questions (although it might be the first 50 percent with the second half). This is often used in combination with dichotomous factors that are scored 0 for inappropriate and 1 for accurate. The Spearman-Brown prophecy method is applied to the correlation to look for the reliability.
- Kuder-Richardson Formula 20 (K-R 20) and Kuder-Richardson Method 21 (K-R 21). These are choice formulas for determining how consistent subject responses are one of the questions on an instrument. Items on the instrument must be dichotomously obtained (0 for inappropriate and 1 for accurate). All items are weighed against each other, somewhat than half the items with the other half of the items. It could be shown mathematically that the Kuder-Richardson trustworthiness coefficient is in fact the mean of all split-half coefficients resulting from different splittings of an test. K-R 21 assumes that of the questions are similarly difficult. K-R 20 does not suppose that.
- Cronbach's Alpha, also called Coefficient Alpha. When the things on a musical instrument are not obtained right versus wrong, Cronbach's alpha is often used to measure the internal consistency. This is the case with attitude musical instruments that use the Likert range. Your computer program such as SPSS is often used to determine Cronbach's alpha. Although Cronbach's alpha is usually used for ratings which fall season along a continuum, it'll produce the same results as KR-20 with dichotomous data (0 or 1).
4 Scorer Arrangement. Performance and product assessments tend to be based on scores by those who are trained to judge the performance or product. The consistency between rating can be calculated in many ways.
- Interrater Stability. Two judges can examine a group of college student products and the relationship between their rankings can be computed (r=. 90 is a common cutoff).
- Percentage Agreement. Two judges can evaluate several products and a share for the number of times they consent is computed (80% is a common cutoff).
All ratings contain problem. The error is what decreases an instrument's reliability: Obtained (also "observed") Rating = True Credit score + Error Report. There could be lots of reasons why the reliability estimation for a measure is low. Four common resources of inconsistencies of test results are recognized: (a) test taker - perhaps the subject matter is having a bad day, (b) test Itself - the questions on the instrument may be unclear, (c) tests conditions - there could be distractions during the tests that detract the topic, (d) test scoring - scorers may be making use of different expectations when evaluating themes' responses.
An device is valid only to the extent that it is scores enable appropriate inferences to be made about (a) a particular group of individuals for (b) specific purposes.
An instrument that is a valid measure of third grader's dialect skills probably is not a valid way of measuring high school student's language skills. An instrument that is clearly a valid predictor of how well students might do in university, may not be a valid way of measuring how well they will do after they complete institution. So we never say an device is valid or not valid. We say it is valid for a particular purpose with a specific group. Validity is specific to the appropriateness of the interpretations we desire to make with the results. For instance, a calculating tape is a valid device to find out people's height; it isn't a valid device to ascertain their weight.
There are three general categories of device validity.
1 Content-Related Data (also known as Face Validity). Specialists in this content measured by the instrument are asked to judge the appropriateness of the things on the instrument. Do they cover the breath of the content area (will the instrument contain a representative test of this content being evaluated)? Are they in a format that is suitable for those using the tool? A test that is intended to gauge the quality of research education in fifth class, should cover materials protected in the fifth quality science course in a way appropriate for fifth graders. A nationwide science test might not be a valid way of measuring local science education, although it might be considered a valid way of measuring national science benchmarks.
2 Criterion-Related Research. Criterion-related proof is collected by assessing the device with some future or current conditions, thus the name criterion-related. The goal of an instrument dictates whether predictive or concurrent validity is warranted.
- Predictive Validity. If a musical instrument is purported to evaluate some future performance, predictive validity should be investigated. An evaluation must be produced between the instrument plus some later behavior so it predicts. Assume a verification test for 5-year-olds is purported to forecast success in kindergarten. To research predictive validity, you might give the prescreening tool to 5-year-olds prior with their entry into kindergarten. The children's kindergarten performance would be assessed at the end of kindergarten and a correlation would be determined between the screening instrument results and the kindergarten performance ratings.
- Concurrent Validity. Concurrent validity compares ratings on an instrument with current performance on various other measure. Unlike predictive validity, where in fact the second way of measuring occurs later, concurrent validity takes a second solution at about the same time. Concurrent validity for a research test could be looked into by correlating results for the test with ratings from another set up science test considered a comparable time. One other way is to manage the instrument to two categories who are known to vary on the trait being measured by the device. You might have support for concurrent validity if the results for the two groups were completely different. An instrument that actions altruism should be able to discriminate those who have it (nuns) from those who don't (homicidal maniacs). You might expect the nuns to report significantly higher on the tool.
3 Construct-Related Evidence. Construct validity is an on-going process. The possible extremes are:
- Discriminant Validity. A musical instrument does not correlate significantly with parameters from which it will differ.
- Convergent Validity. A musical instrument correlates highly with other parameters with which it should theoretically correlate.
Note that recent research has shown the unitary mother nature of the construct of validity.