Seqanswers Leaderboard Ad

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts
  • tujchl
    Member
    • Sep 2009
    • 74

    simple question about Z score and P value in R

    Hi
    I have a list and I calculate Z score and P value in R as below
    Z.score=(0.52-mean(data))/sd(data)
    P.value=2*pnorm(-abs(Z.score))
    and P.value is 0.028 (0.52 is in my list "data")

    but I reverse data and do it in R as below again:
    Z.score=(1/0.52-mean(1/data))/sd(1/data)
    P.value=2*pnorm(-abs(Z.score))
    and P.value is 1.5e-05

    My question is that in my understanding the outcome of these two methods is the same. but now it seems different.
    can you tell me the reason?
  • blancha
    Senior Member
    • May 2013
    • 367

    #2
    I think that by doing the reciprocal transformation, you are drastically changing the distribution shape, hence the drastically different Z scores and p-values.

    The reciprocal transformation preserves the order of the values, but drastically alters the distribution of the values.

    Comment

    • tujchl
      Member
      • Sep 2009
      • 74

      #3
      Hi blancha
      thank you for your replying. your replying helps me a lot.
      just three further questions
      1. I check mean and sd of my data before and after reciprocal transformation. I found that the sd is the same and mean is reciprocal before and after reciprocal transformation. are they evidence to prove your hypothese?
      2. do I have chance to get the same pvalue after some kinds of handling? here I want both of them are 1.5e-05
      3. can I use 1.5e-05 here to prove my value is significant against the distribution?

      Comment

      • blancha
        Senior Member
        • May 2013
        • 367

        #4
        Sorry, I made a small mistake in my previous answer. I wish I could edit it.
        The reciprocal transformation obviously reverses the order of the values.

        1. The standard deviation of the distribution of a set of random numbers after the reciprocal transformation is different. Nor is the mean after transformation the reciprocal of the mean before distribution.

        2. There are transformations that will not affect the shape of the distribution, such as multiplying each value by a constant or adding or subtracting a constant from each value. There are transformations that will affect the shape of the distributions, such as the logarithmic or the square root transformation, but to a much lesser extent than the reciprocal transformation. The logarithmic transformation is commonly used to make highly skewed distributions less skewed.

        3. The reciprocal transformation is the least commonly used. I don't know what your rationale is for picking this transformation, so I can't comment on whether it is appropriate in your case.

        I'm not a statistician. I just use statistics in my work so you may get better answers from a statistician.

        Comment

        Latest Articles

        Collapse

        • seqadmin
          Pathogen Surveillance with Advanced Genomic Tools
          by seqadmin




          The COVID-19 pandemic highlighted the need for proactive pathogen surveillance systems. As ongoing threats like avian influenza and newly emerging infections continue to pose risks, researchers are working to improve how quickly and accurately pathogens can be identified and tracked. In a recent SEQanswers webinar, two experts discussed how next-generation sequencing (NGS) and machine learning are shaping efforts to monitor viral variation and trace the origins of infectious...
          03-24-2025, 11:48 AM
        • seqadmin
          New Genomics Tools and Methods Shared at AGBT 2025
          by seqadmin


          This year’s Advances in Genome Biology and Technology (AGBT) General Meeting commemorated the 25th anniversary of the event at its original venue on Marco Island, Florida. While this year’s event didn’t include high-profile musical performances, the industry announcements and cutting-edge research still drew the attention of leading scientists.

          The Headliner
          The biggest announcement was Roche stepping back into the sequencing platform market. In the years since...
          03-03-2025, 01:39 PM
        • seqadmin
          Investigating the Gut Microbiome Through Diet and Spatial Biology
          by seqadmin




          The human gut contains trillions of microorganisms that impact digestion, immune functions, and overall health1. Despite major breakthroughs, we’re only beginning to understand the full extent of the microbiome’s influence on health and disease. Advances in next-generation sequencing and spatial biology have opened new windows into this complex environment, yet many questions remain. This article highlights two recent studies exploring how diet influences microbial...
          02-24-2025, 06:31 AM

        ad_right_rmr

        Collapse

        News

        Collapse

        Topics Statistics Last Post
        Started by seqadmin, 03-20-2025, 05:03 AM
        0 responses
        41 views
        0 reactions
        Last Post seqadmin  
        Started by seqadmin, 03-19-2025, 07:27 AM
        0 responses
        46 views
        0 reactions
        Last Post seqadmin  
        Started by seqadmin, 03-18-2025, 12:50 PM
        0 responses
        36 views
        0 reactions
        Last Post seqadmin  
        Started by seqadmin, 03-03-2025, 01:15 PM
        0 responses
        191 views
        0 reactions
        Last Post seqadmin  
        Working...