We are given that a recent study showed that the length of time that juries deliberate on a verdict for civil trials is normally distributed with a mean equal to 12.56 hours with a standard deviation of 6.7 hours.

<em>Let X = length of time that juries deliberate on a verdict for civil trials</em>

So, X ~ N( $\mu = 12.56, \sigma^{2} = 6.7^{2}$ )

The z score probability distribution is given by;

Z = $\frac{X-\mu}{\sigma}$ ~ N(0,1)

where, $\mu$ = mean time = 12.56 hours

$\sigma$ = standard deviation = 6.7 hours

So, Probability that deliberation will last between 12 and 15 hours is given by = P(12 hours < X < 15 hours) = P(X < 15) - P(X $\leq$ 12)

P(X < 15) = P( $\frac{X-\mu}{\sigma}$ < $\frac{15-12.56}{6.7}$ ) = P(Z < 0.36) = 0.64058

P(X $\leq$ 12) = P( $\frac{X-\mu}{\sigma}$ $\leq$ $\frac{12-12.56}{6.7}$ ) = P(Z $\leq$ -0.08) = 1 - P(Z < 0.08)

= 1 - 0.53188 = 0.46812

<em>Therefore, P(12 hours < X < 15 hours) = 0.64058 - 0.46812 = 0.1725</em>

Hence, probability that deliberation will last between 12 and 15 hours is 0.1725.

7 0

3 years ago