Z' factor

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Kerstin
Kerstin's picture
Z' factor

I want to know why an assay with a  Z' over 0.5 is defined as a "good assay".

Satinder
Satinder's picture
Dear Kerstin

Dear Kerstin
The Z-factor is a measure of statisticaleffect size. It has been proposed for use in high-throughput screening to judge whether the response in a particular assay is large enough to warrant further attention.

.0
Ideal. Z-factors can never exceed 1.

between 0.5 and 1.0
An excellent assay. Note that if σp = σn, 0.5 is equivalent to a separation of 12 standard deviations between μp and μn.

between 0 and 0.5
A marginal assay.

less than 0
There is too much overlap between the positive and negative controls for the assay to be useful.

 
check the following Refernces for more

  1. Zhang JH, Chung TD, Oldenburg KR, "A Simple Statistical Parameter for Use in Evaluation and Validation of High Throughput Screening Assays." J Biomol Screen. 1999;4(2):67–73.
  2. Sui, Y and Wu, Z, "Alternative Statistical Parameter for High-Throughput Screening Assay Quality Assessment." J Biomol Screen. 2007; 12:229–234.

 

Kerstin
Kerstin's picture
 Hi Satinder,

 Hi Satinder,
thanks for your help!