Question

1. How does reliability helps in performance of maintenance function?

Answer 1

The goal of estimating dependability is to seeabundant|what proportion|what quantity} of the variability in take a look at scores is because oferrors in mensuration and the way much is because of variability in true scores.

Four sensible methods are developed that giveexecutable strategies of estimating take a look at dependability.

1. Test-retest dependability method: directly assesses the degree to that take a look atscores area unit consistent from one take a look at administration to the subsequent.

It involves:

Administering a take a look at to a bunch of people
Re-administering the identical take a look at to the identical cluster at some later time
Correlating the primary set of scores with the second
The correlation between scores on the primarytake a look at and also the scores on the retest is employed to estimate the dependability of the take a look at mistreatment the Pearson product-moment correlation coefficient: conferitem-total correlation.

2. Parallel-forms method:

The key to the present methodology is that thedevelopment of alternate take a look at forms that area unit equivalent in terms of content, response processes and applied mathematics characteristics. as an example, alternate forms exist for many tests of general intelligence, and these tests area unit usually seen equivalent.

With the parallel take a look at model it'sattainable to develop 2 styles of a take a look atthat area unit equivalent within the sense that a person’s true score on type A would be a dead ringer for their true score on type B. If eachstyles of the take a look at were administered to variety of individuals, variations between scores on type A and type B could also be because oferrors in mensuration solely.

It involves:

Administering one kind of the take a look at to a bunch of people
At some later time, administering Associate in Nursing alternate kind of the identical take a look at to the identical cluster of individuals
Correlating scores on type A with scores on typeB
The correlation between scores on the 2alternate forms is employed to estimate the dependability of the take a look at.

This methodology provides a partial resolutionto several of the issues inherent within the test-retest dependability methodology. as an example, since the 2 styles of the take a look atarea unit totally different, carryover result is a smaller amount of a controversy. Reactivity effects also are partly controlled; though taking the primary take a look at might amendmentresponses to the second take a look at. However, it's cheap to assume that the resultwon't be as robust with alternate styles of the take a look at like 2 administrations of the identical take a look at.

However, this system has its disadvantages:

It may be terribly troublesome to make manyalternate styles of a take a look at
It may even be troublesome if not not possibleto ensure that 2 alternate styles of a take a look at area unit parallel measures

3. Split-half method:

This methodology treats the 2 halves of a liveas alternate forms. It provides a straight forward resolution to the matter that the parallel-forms methodology faces: the issue in developing alternate forms.

It involves:

Administering a take a look at to a bunch of people
Splitting the take a look at in 0.5
Correlating scores on one 1/2 the take a look atwith scores on the opposite 1/2 the take a look at
The correlation between these 2 split halves is employed in estimating the dependability of the take a look at. This halves dependability estimate is then stepped up to the total take a look at length mistreatment the Spearman–Brown prediction formula.

There area unit many ways that of cacophonic a take a look at to estimate dependability. as an example, a 40-item vocabulary take a look atmay well be split into 2 subtests, the primaryone created of things one through twenty and also the second created of things twenty onethrough forty. However, the responses from the primary 0.5 could also be consistently totally different from responses within the halfbecause of a rise in item issue and fatigue.

In cacophonic a take a look at, the 2 halves would wish to be as similar as attainable, eachin terms of their content and in terms of the probable state of the respondent. the bestmethodology is to adopt Associate in Nursingodd-even split, within which the odd-numbered things type one 1/2 the take a look at and also the even-numbered things type the opposite. This arrangement guarantees that every 0.5 cancontain Associate in Nursing equal range of things from the start, middle, and finish of the first take a look at.

4. Internal consistency: assesses the consistency of results across things at intervalsa take a look at. the foremost common internal consistency live is Cronbach's alpha, that is sometimes taken because the mean of all attainable split-half coefficients. Cronbach's alpha may be a generalization of Associate in Nursing earlier kind of estimating internal consistency, Kuder–Richardson Formula twenty.[8] though the foremost ordinarily used, there area unit some misconceptions relating toCronbach's alpha.[9][10]

These measures of dependability disagree in their sensitivity to totally different sources of error then needn't be equal. Also, dependability may be a property of the uncountable a liveinstead of the live itself and area unit so sameto be sample dependent. dependability estimates from one sample would possiblydisagree from those of a second sample (beyond what could be expected because ofsampling variations) if the second sample is drawn from {a totally different|a special|a unique|a distinct} population as a result of truthvariability is different during this second population. (This is true of lives of all types—yardsticks would possibly live homes well nevertheless have poor dependability once accustomed measure the lengths of insects.)

Reliability could also be improved by clarity of expression (for written assessments), perpetuation the live, and alternative informal means that. However, formal psychological science analysis, known as item analysis, is taken into account the foremost effective thanks to increase dependability. This analysis consists of computation of item difficulties and item discrimination indices, the latter index involving computation of correlations between the things and total of the item uncountable the complete take a look at. If things that area unittoo troublesome, too easy, and/or have near-zero or negative discrimination area unitreplaced with higher things, the dependability of the live can increase.