Question

The weights of loads hauled by a trucking company approximately follow a bell-shaped (normal) frequency curve with a mean of 15 thousand pounds and a standard deviation of 4 thousand pounds. Note that: 15 ± (1)(4) ==> 11 to 19; 15 ± (2)(4) ==> 7 to 23; 15 ± (3)(4) ==> 3 to 27 . According to the empirical rule, approximately __________ percent of loads weigh between 3 thousand pounds and 27 thousand pounds.

Group of answer choices a)90 b)68 c)95 d)80 e)99.7

Answer 1

Solution:

Given a distribution which is bell-shaped (normal) have

= 15 and = 4

Now ,

3 = 15 - 12 = 15 - (3 * 4) = - 3

27 = 15 + 12 = 15 + (3 * 4) = + 3

Using Empirical rule

P(Between 3 and 27) = P(between - 3 and + 3) = 0.997 = 99.7%

Answer : 99.7

Option e is correct.