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<p>See inline comments below<br>
</p>
<div class="moz-cite-prefix">On 10/01/2021 14:48, Derek M Jones
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:e0281777-d9a6-cd57-4ff0-dee59fc2f53d@knosof.co.uk">Peter,
<br>
<br>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">The PO used some very dodgy
statistical arguments to support their
<br>
reliability claim
<br>
- rebutted in:
<br>
<br>
<a class="moz-txt-link-freetext" href="https://ials.blogs.sas.ac.uk/2019/06/26/the-use-of-statistics-and-software-code/">https://ials.blogs.sas.ac.uk/2019/06/26/the-use-of-statistics-and-software-code/</a>
<br>
<br>
</blockquote>
<br>
I think that both sides got it wrong:
<br>
<a class="moz-txt-link-freetext" href="http://shape-of-code.coding-guidelines.com/2021/01/07/likelihood-of-a-fault-experience-when-using-the-horizon-it-system/">http://shape-of-code.coding-guidelines.com/2021/01/07/likelihood-of-a-fault-experience-when-using-the-horizon-it-system/</a>
<br>
<br>
<br>
</blockquote>
In what way did the other side get wrong?
<br>
</blockquote>
<br>
They both assumed there was enough information available to
calculate
<br>
the likelihood of a fault being experienced.
<br>
<br>
<blockquote type="cite">Most of the material submitted identified
fallacies in the PO
<br>
statistical arguments
<br>
(including the lottery analogy that you included the Shape of
Code
<br>
document).
<br>
</blockquote>
<br>
This argument does not appear in the links you gave or the Ladkin
et al
<br>
papers. Do you have a reference?
<br>
</blockquote>
<p>It is in the reference I gave</p>
<p><a class="moz-txt-link-freetext" href="https://ials.blogs.sas.ac.uk/2019/06/26/the-use-of-statistics-and-software-code/">https://ials.blogs.sas.ac.uk/2019/06/26/the-use-of-statistics-and-software-code/</a>
<br>
</p>
<p>See abstract below:<br>
</p>
<h3 style="box-sizing: border-box; margin: 0px; padding: 0px 0px
10px; border: 0px; outline: 0px; font-size: 22px;
text-size-adjust: 100%; vertical-align: baseline; background:
rgb(255, 255, 255); color: rgb(51, 51, 51); line-height: 1em;
font-weight: 500; font-family: "Open Sans", Arial,
sans-serif; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; letter-spacing: normal; orphans: 2;
text-align: left; text-indent: 0px; text-transform: none;
white-space: normal; widows: 2; word-spacing: 0px;
-webkit-text-stroke-width: 0px; text-decoration-thickness:
initial; text-decoration-style: initial; text-decoration-color:
initial;">Discussion and conclusions</h3>
<p style="box-sizing: border-box; margin: 0px; padding: 0px 0px 1em;
border: 0px; outline: 0px; font-size: 14px; text-size-adjust:
100%; vertical-align: baseline; background: rgb(255, 255, 255);
color: rgb(140, 140, 140); font-family: "Open Sans",
Arial, sans-serif; font-style: normal; font-variant-ligatures:
normal; font-variant-caps: normal; font-weight: 500;
letter-spacing: normal; orphans: 2; text-align: left; text-indent:
0px; text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration-thickness: initial; text-decoration-style:
initial; text-decoration-color: initial;">I find it amazing that
Dr Worden’s seriously flawed analysis could be viewed as credible
evidence in a court of law.</p>
<p style="box-sizing: border-box; margin: 0px; padding: 0px 0px 1em;
border: 0px none; outline: currentcolor none 0px; font-size: 14px;
vertical-align: baseline; background: rgb(255, 255, 255) none
repeat scroll 0% 0%; font-family: "Open Sans", Arial,
sans-serif; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; letter-spacing: normal; text-align:
left; text-indent: 0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration-thickness: initial; text-decoration-style:
initial; text-decoration-color: initial;"><font color="darkblue">Looking
at the probability that an account submission can fail and
saying it is tiny is meaningless on its own. By analogy, it is
illogical to say that if there is only a 1 in a million chance
of winning a lottery, ergo any person who claims to have won the
lottery must be lying. This argument ignores the fact that
increasing the number of people who buy tickets will increase
the probability that somebody will win (even if your own chances
remain the same). For example, if we know that 10 million people
buy tickets, we would not be at all surprised to hear the 10
people won the lottery that week.</font></p>
<p style="box-sizing: border-box; margin: 0px; padding: 0px 0px 1em;
border: 0px; outline: 0px; font-size: 14px; text-size-adjust:
100%; vertical-align: baseline; background: rgb(255, 255, 255);
color: rgb(140, 140, 140); font-family: "Open Sans",
Arial, sans-serif; font-style: normal; font-variant-ligatures:
normal; font-variant-caps: normal; font-weight: 500;
letter-spacing: normal; orphans: 2; text-align: left; text-indent:
0px; text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration-thickness: initial; text-decoration-style:
initial; text-decoration-color: initial;">To perform a statistical
analysis to determine whether the claimant’s claims are credible,
we should start from the hypothesis that all branches are
potential victims of random Horizon failures, then ask what
conditions are needed to produce 500 victims and then consider
whether these conditions are credible.</p>
<p style="box-sizing: border-box; margin: 0px; padding: 0px 0px 1em;
border: 0px; outline: 0px; font-size: 14px; text-size-adjust:
100%; vertical-align: baseline; background: rgb(255, 255, 255);
color: rgb(140, 140, 140); font-family: "Open Sans",
Arial, sans-serif; font-style: normal; font-variant-ligatures:
normal; font-variant-caps: normal; font-weight: 500;
letter-spacing: normal; orphans: 2; text-align: left; text-indent:
0px; text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration-thickness: initial; text-decoration-style:
initial; text-decoration-color: initial;">We showed that only 31
bugs similar to the Suspense Account bug are needed to cause
submission failure in 500 branches. This number of residual bugs
is entirely credible for a complex real-time system, and in
practice there could be many more than this (even in a mature
20-year-old system).</p>
<p style="box-sizing: border-box; margin: 0px; padding: 0px 0px 1em;
border: 0px; outline: 0px; font-size: 14px; text-size-adjust:
100%; vertical-align: baseline; background: rgb(255, 255, 255);
color: rgb(140, 140, 140); font-family: "Open Sans",
Arial, sans-serif; font-style: normal; font-variant-ligatures:
normal; font-variant-caps: normal; font-weight: 500;
letter-spacing: normal; orphans: 2; text-align: left; text-indent:
0px; text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration-thickness: initial; text-decoration-style:
initial; text-decoration-color: initial;">As a result of these
analyses we consider that it is entirely credible that issues
experienced by the 500 claimants could have been caused by flaws
in the Horizon software.</p>
<pre class="moz-signature" cols="72">--
Peter Bishop
Chief Scientist
Adelard LLP
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