# How do you interpret test-retest reliability scores?

## How do you interpret test-retest reliability scores?

Test-retest reliability coefficients (also called coefficients of stability) vary between 0 and 1, where:

1. 1 : perfect reliability,
2. ≥ 0.9: excellent reliability,
3. ≥ 0.8 < 0.9: good reliability,
4. ≥ 0.7 < 0.8: acceptable reliability,
5. ≥ 0.6 < 0.7: questionable reliability,
6. ≥ 0.5 < 0.6: poor reliability,

## What is a good test-retest reliability coefficient?

The closer each respondent’s scores are on T1 and T2, the more reliable the test measure (and the higher the coefficient of stability will be). 0.9 and greater: excellent reliability. Between 0.9 and 0.8: good reliability. Between 0.8 and 0.7: acceptable reliability.

What does it mean if test-retest reliability is low?

So if the test–retest reliability coefficient is low, it is unknown whether the test is unreliable or differential systematic factors are at work. One way to minimize carryover effects would be to increase the time interval between the two administrations of the test.

What does a reliability coefficient of 0.80 mean?

As a general rule, a reliability of 0.80 or higher is desirable for instructor-made tests. The higher the reliability estimated for the test, the more confident one may feel that the discriminations between students scoring at different score levels on the test are, in fact, stable differences.

### What is acceptable Cronbach’s alpha?

A general accepted rule is that α of 0.6-0.7 indicates an acceptable level of reliability, and 0.8 or greater a very good level. However, values higher than 0.95 are not necessarily good, since they might be an indication of redundance.

### What is agreement in Bland Altman?

The Bland–Altman method calculates the mean difference between two methods of measurement (the ‘bias’), and 95% limits of agreement as the mean difference (2 sd) [or more precisely (1.96 sd)]. The presentation of the 95% limits of agreement is for visual judgement of how well two methods of measurement agree.

What does a reliability coefficient of 0.90 mean?

The symbol for reliability coefficient is letter r. An acceptable reliability coefficient must not be below 0.90, less than this value indicates inadequate reliability. For instance, r =. 90 on a test means that 90% of the test score is accurate while the remaining 10% consists of standard error.

What is considered a high reliability coefficient?

The values for reliability coefficients range from 0 to 1.0. A coefficient of 0 means no reliability and 1.0 means perfect reliability. 80, it is said to have very good reliability; if it is below . 50, it would not be considered a very reliable test.

#### How do you interpret Cronbach Alpha results?

Theoretically, Cronbach’s alpha results should give you a number from 0 to 1, but you can get negative numbers as well. A negative number indicates that something is wrong with your data—perhaps you forgot to reverse score some items. The general rule of thumb is that a Cronbach’s alpha of . 70 and above is good, .

#### When to use paired ttest and Bland Altman plots?

Historically, Pearson correlation coefficient, paired ttest, and Bland-Altman plot have been used to evaluate reliability.3, 6, 7, 8However, paired ttest and Bland-Altman plot are methods for analyzing agreement, and Pearson correlation coefficient is only a measure of correlation, and hence, they are nonideal measures of reliability.

How is the bland and Altman method used?

The analysis of differences: the Bland and Altman method. They established a method to quantify agreement between two quantitative measurements by constructing limits of agreement. These statistical limits are calculated by using the mean and the standard deviation ( s) of the differences between two measurements.

What is the Bland Altman plot in Excel?

In order to more readily see the difference between the two measurement instruments, it is useful to plot the means of each pair of measurements (x value) versus the difference between the measurements (y value). This is called a Bland-Altman Plot, and is shown in Figure 2.

## Which is a more desirable measure of reliability?

A more desirable measure of reliability should reflect both degree of correlation and agreement between measurements. Intraclass correlation coefficient (ICC) is such as an index. Table 1 Hypothetical Flexion-Extension Range of Motion (ROM) of L4-L5 Measured by Radiograph