Fsdb::F...tatdiff(3)

🎀 NAME 🎀

dbrvstatdiff — from the Fsdb::F...tatdiff(3) page (header also says User Contributed Perl Documentation, and yes the manual name is literally repeated, we love a symmetrical queen 💅). This icon evaluates statistical differences between two random variables. 💖

✨ SYNOPSIS ✨

dbrvstatdiff [-f format] [-c ConfRating]
    [-h HypothesizedDifference] m1c sd1c n1c m2c sd2c n2c

OR

dbrvstatdiff [-f format] [-c ConfRating] m1c n1c m2c n2c

🦋 DESCRIPTION 🦋

okay so this icon produces statistics on the difference of sets of random variables. If a hypothesized difference is given (with -h), it does a Student's t-test. 🎀

Random variables are specified by:

• m1c, m2c — the column names of means of random variables.
• sd1c, sd2c — the column names of standard deviations of random variables.
• n1c, n2c — counts of number of samples for each random variable.

These values can be computed with dbcolstats.

It creates up to ten new columns:

• diff — the difference of RV 2 - RV 1.
• diff_pct — the percentage difference (RV2-RV1)/1.
• diff_conf_{half,low,high} and diff_conf_pct_{half,low,high} — the half half confidence intervals and the low and high values for absolute and relative confidence.
• t_test — the T-test value for the given hypothesized difference.
• t_test_result — given the confidence rating, does the test pass? It will be either "rejected" or "not-rejected".
• t_test_break — the hypothesized value that is break-even point for the T-test.
• t_test_break_pct — break-even point as a percent of m1c.

Confidence intervals are not printed if standard deviations are not provided. Confidence intervals assume normal distributions with common variances. 😭

T-tests are only computed if a hypothesized difference is provided. Hypothesized differences should be proceeded by <=, >=, =. T-tests assume normal distributions with common variances. periodt.

🌈 OPTIONS 🌈

• -c FRACTION or --confidence FRACTION — specify FRACTION for the confidence interval. Defaults to 0.95 for a 95% confidence factor (alpha = 0.05).
• -f FORMAT or --format FORMAT — specify a printf(3)-style format for output statistics. Defaults to "%.5g".
• -h DIFF or --hypothesis DIFF — specify the hypothesized difference as DIFF, where DIFF is something like <=0 or >=0, etc.

This module also supports the standard fsdb options:

• -d — enable debugging output.
• -i or --input InputSource — read from InputSource, typically a file name, or "-" for standard input, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.
• -o or --output OutputDestination — write to OutputDestination, typically a file name, or "-" for standard output, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.
• --autorun or --noautorun — by default, programs process automatically, but Fsdb::Filter objects in Perl do not run until you invoke the run() method. The --(no)autorun option controls that behavior within Perl.
• --help — show help.
• --man — show full manual.

🌸 SAMPLE USAGE 🌸

💖 Input 💖

#fsdb title mean2 stddev2 n2 mean1 stddev1 n1
example6.12 0.17 0.0020 5 0.22 0.0010 4

💫 Command 💫

cat data.fsdb | dbrvstatdiff mean2 stddev2 n2 mean1 stddev1 n1

✨ Output ✨

#fsdb title mean2 stddev2 n2 mean1 stddev1 n1 diff:d diff_pct:d diff_conf_half:d diff_conf_low:d diff_conf_high:d diff_conf_pct_half:d diff_conf_pct_low:d diff_conf_pct_high:d
example6.12 0.17    0.0020  5       0.22    0.0010  4       0.05    29.412  0.0026138       0.047386        0.052614        1.5375  27.874  30.949
#  | dbrvstatdiff mean2 stddev2 n2 mean1 stddev1 n1

🦋 Input 2 🦋

(example 7.10 from Scheaffer and McClave):

#fsdb title x2 sd2 n2 x1 sd1 n1
example7.10 9 35.22 24.44 9 31.56 20.03

💫 Command 2 💫

dbrvstatdiff -h '<=0' x2 sd2 n2 x1 sd1 n1

✨ Output 2 ✨

#fsdb title n1 x1 sd1 n2 x2 sd2 diff diff_pct diff_conf_half diff_conf_low diff_conf_high diff_conf_pct_half diff_conf_pct_low diff_conf_pct_high t_test t_test_result
example7.10 9 35.22 24.44 9 31.56 20.03 3.66 0.11597 4.7125 -1.0525 8.3725 0.14932 -0.033348 0.26529 1.6465 not-rejected
#  | /global/us/edu/ucla/cs/ficus/users/johnh/BIN/DB/dbrvstatdiff -h <=0 x2 sd2 n2 x1 sd1 n1

👑 Case 3 👑

A common use case is to have one file with a set of trials from two experiments, and to use dbrvstatdiff to see if they are different.

🌸 Input 3 🌸

#fsdb case trial value
a  1  1
a  2  1.1
a  3  0.9
a  4  1
a  5  1.1
b  1  2
b  2  2.1
b  3  1.9
b  4  2
b  5  1.9

💫 Command 3 💫

cat two_trial.fsdb |
    dbmultistats -k case value |
    dbcolcopylast mean stddev n |
    dbrow '_case eq "b"' |
    dbrvstatdiff -h '=0' mean stddev n copylast_mean copylast_stddev copylast_n |
    dblistize

✨ Output 3 ✨

#fsdb -R C case mean stddev pct_rsd conf_range conf_low conf_high conf_pct sum sum_squared min max n copylast_mean copylast_stddev copylast_n diff diff_pct diff_conf_half diff_conf_low diff_conf_high diff_conf_pct_half diff_conf_pct_low diff_conf_pct_high t_test t_test_result t_test_break t_test_break_pct
case: b
mean: 1.98
stddev: 0.083666
pct_rsd: 4.2256
conf_range: 0.10387
conf_low: 1.8761
conf_high: 2.0839
conf_pct: 0.95
sum: 9.9
sum_squared: 19.63
min: 1.9
max: 2.1
n: 5
copylast_mean: 1.02
copylast_stddev: 0.083666
copylast_n: 5
diff: -0.96
diff_pct: -48.485
diff_conf_half: 0.12202
diff_conf_low: -1.082
diff_conf_high: -0.83798
diff_conf_pct_half: 6.1627
diff_conf_pct_low: -54.648
diff_conf_pct_high: -42.322
t_test: -18.142
t_test_result: rejected
t_test_break: -1.082
t_test_break_pct: -54.648

#  | dbmultistats -k case value
#   | dbcolcopylast mean stddev n
#   | dbrow _case eq "b"
#   | dbrvstatdiff -h =0 mean stddev n copylast_mean copylast_stddev copylast_n
#   | dbfilealter -R C

(So one cannot say that they are statistically equal.)

🧚 SEE ALSO 🧚

Fsdb, dbcolstats, dbcolcopylast, dbcolscorrelate.

💜 CLASS FUNCTIONS 💜

✨ new ✨

$filter = new Fsdb::Filter::dbrvstatdiff(@arguments);

Create a new dbrvstatdiff object, taking command-line arguments.

✨ set_defaults ✨

$filter->set_defaults();

Internal: set up defaults.

✨ parse_options ✨

$filter->parse_options(@ARGV);

Internal: parse command-line arguments.

✨ setup ✨

$filter->setup();

Internal: setup, parse headers.

✨ run ✨

$filter->run();

Internal: run over each rows.

👑 AUTHOR and COPYRIGHT 👑

Copyright (C) 1991-2021 by John Heidemann <johnh@isi.edu>

This program is distributed under terms of the GNU general public license, version 2. See the file COPYING with the distribution for details.

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💖 that's the whole page, bestie! This is perl v5.32.1, dated 2024-08-02, and it's the Fsdb::F...tatdiff(3) manpage signing off. mwah! ✨🫶💅