Baltimore officials discovered 107 million orb-weaving spiders had infested a disused water treatment plant, according to an entomology society website. If the spiders' weights are Normally distributed with mean 11 grams and standard deviation 2 grams, approximately how many spiders in the colony weigh more than 12 grams?

Question

Quizplus · Accepted Answer

To find the number of spiders weighing more than 12 grams, we need to find the area under the normal curve to the right of 12.

Using a standard normal distribution table or calculator, we can find the z-score:

z = (12 - 11) / 2 = 0.5

Looking up the area to the right of z = 0.5, we find it to be 0.3085.

To find the number of spiders, we can multiply this probability by the total number of spiders:

0.3085 x 107,000,000 = 33,006,950

Rounding to the nearest thousand, we get 33,000,000 spiders weighing more than 12 grams. Therefore, the best choice is D.

Baltimore Officials Discovered 107 Million Orb-Weaving Spiders Had Infested a Disused