# Questions tagged [d-prime]

d' (also called sensitivity index) is a measure used in signal detection theory to quantify how well a signal can be distinguished from noise.

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### Calculating d prime in SPSS - Signal Detection

I have conducted an experiment in which participants saw one figure (target) briefly followed by a figure (probe) and asked if they were the same (yes) or not (no). Five different figures total, and ...
25 views

### Understanding and implementing the dprime measure in Python

According to Wikipedia, the dprime score (aka 'sensitivity index') can be expressed as $$d' = Z(\text{hit rate}) - Z(\text{false alarm rate})$$ hit rate (aka recall aka sensitivity) and false alarm ...
50 views

### ROC curve, d' A' - assumption-free?

In my research I want to know how reliably certain feature of a sentence indicates the class that sentence belongs to. So, according to that feature (=how many elements X they contain), the ...
78 views

### d prime correction to use with a low number of trials

I am doing a psycholinguistic experiment, where I want to calculate d’ for each participant’s test scores. In the test, participants listen to 4 familiar words and 8 novel distractor words, and have ...
269 views

### How do I calculate d' from experimental data?

In Signal Detection Theory, d' is defined by the z-scores of Hits and False Alarms: d' = z(Hits) - z(False Alarms). Say the task is to detect if a certain object is present in a series of pictures, ...
73 views

### Is there an accepted way to interpret d' (d-prime) for evidence of detection

I have run a learning experiment, with a yes-no familiarity test at the end, and computed d' across various conditions. Is there some rule of thumb (perhaps dependent on sample size) as to how d' ...
2k views

### Connections between $d^\prime$ (d-prime) and AUC (Area Under the ROC Curve); underlying assumptions

In machine learning we may use the area under the ROC curve (often abbreviated AUC, or AUROC) to summarise how well a system can discriminate between two categories. In signal detection theory often ...
320 views

### A' (A prime) for extreme Hit rates and False Alarms

I am trying to compute the non parametric measure of sensitivity A' according to the following formula reported by Stanislav & Todorov (1999):  A'= .5+sign(H-F)*((H-F)^2+abs(H-F))/(4*max(H,F)-4*...
13k views

### d prime with 100% hit rate probability and 0% false alarm probability

I would like to calculate d prime for a memory task that involves detecting old and new items. The problem I have is that some of the subjects have hit rate of 1 and/or false alarm rate of 0, which ...
881 views

### Negative D-prime values; use absolute values?

I have calculated D-prime measurements for for a memory performance task. Subjects viewed images that were either old or new and had to indicate their response via a button press. Thus, their response ...
In signal detection theory, people often use $d'$ to assess performance. Apart from the fact that $d'$ is in $z$ units (units of measurement transformed to standard deviation units, i.e., $z$ scores), ...