Dataplot Vol 2 Vol 1

# PRECISION

Name:
PRECISION (LET)
Type:
Let Subcommand
Purpose:
Compute the precision of a variable.
Description:
The sample precision is defined as the reciprocal of the sample variance. That is

$$\mbox{Precision} = \frac{n-1} {\sum_{i=1}^{n}{(X_{i} - \bar{x})^2}}$$

where n and $$\bar{x}$$ denote the sample size and sample mean, respectively.

Note that high variance implies low precision while low variance implies high precision.

Some sources define the precision as the reciprocal of the standard deviation.

Syntax 1:
LET <par> = PRECISION <y>             <SUBSET/EXCEPT/FOR qualification>
where <y> is a response variable;
<par> is a parameter where the precision value is saved;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.
Syntax 2:
LET <par> = DIFFERENCE OF PRECISION <y1> <y2>             <SUBSET/EXCEPT/FOR qualification>
where <y1> is the first response variable;
<y2> is the second response variable;
<par> is a parameter where the difference of the precision values is saved;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.
Examples:
LET PREC = PRECISION Y1
LET PREC = PRECISION Y1 SUBSET TAG > 2

LET PREC = DIFFERENCE OF PRECISION Y1 Y2

Note:
Dataplot statistics can be used in a number of commands. For details, enter

Default:
None
Synonyms:
None
Related Commands:
 VARIANCE = Compute the variance of a variable. MEAN = Compute the mean of a variable. STANDARD DEVIATION = Compute the standard deviation of a variable.
Applications:
Data Analysis
Implementation Date:
2017/01
2017/03: Added DIFFERENCE OF PRECISION
Program 1:

SKIP 25
READ ZARR13.DAT Y
LET P = PRECISION Y

Program 2:

. Step 1:   Create the data
.
skip 25
read gear.dat y x
skip 0
.
char X
line blank
y1label Precision
x1label Group
x1tic mark offset 0.5 0.5
label case asis
title case asis
title Precision of GEAR.DAT
title offset 2
.
set statistic plot reference line average
precision plot y x
.
set write decimals 5
tabulate precision y x



Cross Tabulate PRECISION

(Response Variables: Y        )
---------------------------------------------
X          |         PRECISION
---------------------------------------------
1.00000   |       52941.17647
2.00000   |       36749.69375
3.00000   |       63202.24719
4.00000   |       67365.26946
5.00000   |       17411.49158
6.00000   |       10231.92360
7.00000   |       16114.59266
8.00000   |       76013.51351
9.00000   |       58403.63400
10.00000   |       35211.26761

Program 3:

SKIP 25
READ IRIS.DAT Y1 TO Y4 X
.
LET A = DIFFERENCE OF PRECISION Y1 Y2
SET WRITE DECIMALS 4
TABULATE DIFFERENCE OF PRECISION Y1 Y2 X

Cross Tabulate DIFFERENCE OF PRECISION

(Response Variables: Y1       Y2      )
---------------------------------------------
X          |   DIFFERENCE OF P
---------------------------------------------
1.0000   |            1.0889
2.0000   |           -6.4021
3.0000   |           -7.1419

.
XTIC OFFSET 0.2 0.2
X1LABEL GROUP ID
Y1LABEL DIFFERENCE OF PRECISION
CHAR X
LINE BLANK
DIFFERENCE OF PRECISION PLOT Y1 Y2 X

CHAR X ALL
LINE BLANK ALL
BOOTSTRAP DIFFERENCE OF PRECISION PLOT Y1 Y2 X


NIST is an agency of the U.S. Commerce Department.

Date created: 01/24/2017
Last updated: 06/30/2017

Please email comments on this WWW page to alan.heckert@nist.gov.