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    Subject[PATCH 06/21] perf, stat: FIXME Stddev calculation is incorrect
    Date
    Fix the standard deviation calculation.  The current calculation
    does the standard deviation mean which is slightly different.

    Signed-off-by: Don Zickus <dzickus@redhat.com>
    ---
    tools/perf/util/stat.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
    index 6506b3d..58aa661 100644
    --- a/tools/perf/util/stat.c
    +++ b/tools/perf/util/stat.c
    @@ -47,7 +47,8 @@ double stddev_stats(struct stats *stats)
    return 0.0;

    variance = stats->M2 / (stats->n - 1);
    - variance_mean = variance / stats->n;
    + //variance_mean = variance / stats->n;
    + variance_mean = variance;

    return sqrt(variance_mean);
    }
    --
    1.7.11.7


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