title: samr analysis: How to interpret Median FDR/90th perc FDR=0.000000?
body: <p>I am performing significance analysis of microarray (SAM) using the <a href="https://statweb.stanford.edu/~tibs/SAM/" rel="nofollow noreferrer">samr</a> package in R. </p>
  
  <p>I have some doubts regarding the reported "Median FDR" and "90th perc FDR" values, as illustrated in the following:</p>
  
  <pre><code>samr.obj &lt;- samr(data1,
              resp.type = "Two class unpaired",
              assay.type = "array",
              nperms=1000,
              center.arrays=TRUE,
              testStatistic = "standard",
              random.seed=42)
  delta.table &lt;- samr.compute.delta.table(samr.obj)
  </code></pre>
  
  <p>An excerpt of delta.table:</p>
  
  <pre><code>print(delta.table[,1:6])
  
        delta           #med false pos  #90th perc false pos #called median FDR 90th perc FDR
  [22,] 0.869597977       1.0666667            2.400000       31 0.03440860    0.07741935
  [23,] 0.954388709       0.8000000            2.133333       30 0.02666667    0.07111111
  [24,] 1.043123196       0.2666667            1.333333       25 0.01066667    0.05333333
  [25,] 1.135801439       0.0000000            0.000000        6 0.00000000    0.00000000
  </code></pre>
  
  <p><strong>My question</strong>:</p>
  
  <p>How to interpret line <code>[25, ]</code> having <code>"Median FDR"= 0.000000</code> and <code>"90th perc FDR"= 0.000000</code>? Is the corrected p-value "so small" it is actually rounded? Or should be considered an error?</p>