Question

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. Given this information, what is the probability that deliberation will last between 12 and 15 hours?

Answer 1

Answer:

Probability that deliberation will last between 12 and 15 hours is 0.1725.

Step-by-step explanation:

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.

Let X = length of time that juries deliberate on a verdict for civil trials

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

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

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