# A question about the confidence interval of objective audio quality (e.g. PEAQ), thans very much. (Junyong You )

```Subject: A question about the confidence interval of objective audio quality (e.g. PEAQ), thans very much.
From:    Junyong You  <junyong.you@xxxxxxxx>
Date:    Mon, 27 Oct 2008 12:17:07 +0200
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

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Hi All,

=20

I have a question about the confidence interval (CI) of the objective =
audio quality. Of course, CI should be a concept with the subjective =
quality scores. However, once we compute the objective score using one =
audio quality metric (such as PEAQ, PESQ, NMR, whatever), how much is =
this objective score believable with respect to the real quality, =
supposing we don't know the real quality. For example, if the objective =
PEAQ score is -1.5, can we believe the magnitude of the real quality is =
[-2~-1]?

=20

I tried to compute the CI by using the standard samples for PEAQ as =
following: the objective quality (ODG) is computed for each sample =
firstly, and then the difference (D) between ODG and subjective quality =
(SDG) is gotten, for all samples. I assume the difference D is =
approximately normally distributed, so the CI (e.g. 95%) of D can be =
computed according to the T-distribution table, standard deviation of D, =
and sample amount. For example, for PEAQ, the computed 95% CI is 0.16. =
Then, if the ODG of one sequence is computed by using PEAQ, can we think =
the subjective quality SDG should belong to the interval [ODG-0.16, =
ODG+0.16] with the probability 95%? Is this way to compute the CI of =
objective quality right?

=20

=20

Best regards,

=20

Junyong You

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EN-US">Hi=20
All,</SPAN><SPAN lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'; =
mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: =
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<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt; LINE-HEIGHT: =
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lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'; =
mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: =
EN-US">&nbsp;<o:p></o:p></SPAN></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt; LINE-HEIGHT: =
normal"><SPAN=20
lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; mso-ascii-font-family: Calibri; =
mso-fareast-font-family: 'Times New Roman'; mso-hansi-font-family: =
Calibri; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: =
EN-US">I=20
have a question about the confidence interval (CI) of the objective =
audio=20
quality. Of course, CI should be a concept with the subjective quality =
scores.=20
However, once we compute the objective score using one audio quality =
metric=20
(such as PEAQ, PESQ, NMR, whatever), how much is this objective score =
believable=20
with respect to the real quality, supposing we don=92t know the real =
quality. For=20
example, if the objective PEAQ score is -1.5, can we believe the =
magnitude of=20
the real quality is [-2~-1]?</SPAN><SPAN lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'; =
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<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt; LINE-HEIGHT: =
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lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'; =
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<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt; LINE-HEIGHT: =
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lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; mso-ascii-font-family: Calibri; =
mso-fareast-font-family: 'Times New Roman'; mso-hansi-font-family: =
Calibri; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: =
EN-US">I=20
tried to compute the CI by using the standard samples for PEAQ as =
following: the=20
objective quality (ODG) is computed for each sample firstly, and then =
the=20
difference (D) between ODG and subjective quality (SDG) is gotten, for =
all=20
samples. I assume the difference D is approximately normally =
distributed, so the=20
CI (e.g. 95%) of D can be computed according to the T-distribution =
table,=20
standard deviation of D, and sample amount. For example, for PEAQ, the =
computed=20
95% CI is 0.16. Then, if the ODG of one sequence is computed by using =
PEAQ, can=20
we think the subjective quality SDG should belong to the interval =
[ODG-0.16,=20
ODG+0.16] with the probability 95%? Is this way to compute the CI of =
objective=20
quality right?</SPAN><SPAN lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'; =
mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: =
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lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'; =
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EN-US">&nbsp;<o:p></o:p></SPAN></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt; LINE-HEIGHT: =
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lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; mso-ascii-font-family: Calibri; =
mso-fareast-font-family: 'Times New Roman'; mso-hansi-font-family: =
Calibri; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: =
EN-US">I=20
much.<o:p></o:p></SPAN></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt; LINE-HEIGHT: =
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lang=3DEN-US=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman','serif'; =
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mso-fareast-font-family: 'Times New Roman'; mso-hansi-font-family: =
Calibri; mso-bidi-font-family: 'Times New Roman'">Best=20
regards,</SPAN><SPAN=20
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mso-fareast-font-family: 'Times New Roman'; mso-hansi-font-family: =
Calibri; mso-bidi-font-family: 'Times New Roman'">Junyong=20
You</SPAN></P></DIV></BODY></HTML>

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