Reasonable Doubt as Alpha Level
Recall that social scientists provide evidence based on probability or alpha levels -- the lower the alpha level, the more evidence needed to prove a theory -- a common alpha level for the social sciences would be .05, meaning that a researcher will make a conclusion that their theory is correct when they feel 95% or more certain about their evidence...
The OJ jury would only accept the prosecution's theory that OJ is guilty only if all twelve members conclude beyond a reasonable doubt that OJ did indeed commit the murders...
As in the social sciences, there is a tension in the judicial system between the prosecutor's ability to provide evidence for their case (power) and the jury's feelings about returning a gulity verdict (significance or alpha level)....
Standard of Innocent Until Proven Guilty
The standard of reasonable doubt may vary from jury to jury and case to case, but generally, juries, unlike social scientists, may be more likely to make (or feel comfortable with) a Type II Error based on the notion of "innocent until proven guilty."
The Jury's Low Alpha Level
In such a high profile double murder trial as this, the jury most likely abided by very strict and rigid standards when assessing levels of reasonable doubt concerning the evidence linking OJ to the murders...this means the juryÕs alpha level was probably very low, maybe .01 -- meaning they wanted to be 99% sure that their conclusion matches reality...
...As a result, Marcia and Chris had a harder time getting their theory accepted by the jury -- they had to increase the amount (sample size) and the persuasiveness (effect size) of their evidence in order to increase the chances that the jury would conclude that their theory is indeed the correct theory (power)...
