[SPSS Video #9: Obtaining An ROC Curve In SPSS

Psychometric testing explained

Duration: 00:02:14

This video will demonstrate how to obtain an roc curve the data for this example comes from a study that wanted to distinguish delirium from dementia patients on the basis of levels of serum markers in particular we will look at interleukin-6 an inflammatory cytokine which plays a role in fighting infection

To get an roc curve select analyze and then roc curve in the new window move delirium to the state variable it is coded one for delirium and zero for dementia so we enter one for the value of state variable next we move il6 to the test variable box

In the display box we’ll check with diagonal reference line and coordinate points of the roc curve here is the roc curve the x-axis shows one minus specificity which is the false positive rate and the y-axis gives the sensitivity we want to find a point on the curve

With high sensitivity and low one minus specificity the closer to the upper left corner the better this looks like an ideal point the area under the curve is 0.812 which is above 0.5 equivalent to chance and represented by the reference line the coordinates of the curve show the

Sensitivity and 1 minus specificity for varying cut points if we choose 2.265 as a cup point the sensitivity is 0.737 and 1 minus specificity is 0.136 and that corresponds to the the ideal point we saw earlier this completes the demonstration of obtaining an roc curve

spss-video-9-obtaining-an-roc-curve-in-spss

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