Exam 13: Normal Distributions

The weights of cockroaches follow a Normal distribution with mean 80 grams and standard deviation 2 grams. The figure below is the Normal curve for this distribution of weights. Point C on this Normal curve corresponds to

The 34th percentile of a distribution is

The weight losses for participants in a large exercise and diet study vary according to a Normal distribution with mean 14.5 pounds and standard deviation 3 pounds. Approximately one-half of the participants in the study lose more than:

Scores of adults on the Wechsler Adult Intelligence Scale (a common IQ test) follow a Normal distribution. The middle 95% of scores on this test range from 70 to 130. What is the standard deviation of the test scores?

A number with 60% of the data above it is

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?

Suppose that the Blood Alcohol Content (BAC) of students who drink five beers varies from student to student according to a Normal distribution with mean 0.07 and standard deviation 0.01. What percent of students who drink five beers have a BAC above 0.08 (the legal limit for driving in most states)?

The weight losses for participants in a large exercise and diet study vary according to a Normal distribution with mean 14.5 pounds and standard deviation 3 pounds. Approximately what percent of the participants lose more than 20.5 pounds?

Suppose that the distribution of heart rates for medium-sized dogs is Normally distributed with mean 115 beats per minute and standard deviation 18 beats per minute. Stacy learns from the veterinarian that dogs with heart rates in the upper 8% may be in danger of heart failure. For medium-sized dogs, a dangerous heart rate would be one above what value?

Scores on the American College Testing (ACT) college entrance exam follow the Normal distribution with mean 18 and standard deviation 6. Wayne's standard score on the ACT was -1.1. Wayne scored better than approximately

Suppose that the distribution of heart rates for medium-sized dogs is Normally distributed with mean 115 beats per minute and standard deviation 18 beats per minute. Stacy takes her medium-sized dog, Scooter, to the veterinarian for a wellness check and learns that Scooter's heart rate is 126 beats per minute. Approximately what percentage of medium-sized dogs have a heart rate that is lower than Scooter's?

What percent of the observations from a Normal distribution lie between a standard score of -1 and a standard score of 2? (Hint: sketch a Normal curve.)

A (statistically savvy) local angler remarks that the weights of the blue gill (fish) caught from Big Bass Lake are Normally distributed. He doesn't remember the mean or the standard deviation, but he does remember that the first quartile is 2 pounds, 2 ounces and the third quartile is 3 pounds, 6 ounces. The standard deviation of blue gill weights is closest to:

Two measures of center are marked on the density curve below.

Scores of adults aged 60 to 64 on a common IQ test are approximately Normally distributed with mean 90 and standard deviation 15. Suppose we call an IQ of 90 "normal" for adults aged 60 to 64. What percent of the population have "below normal" IQs?

The 50th percentile of a distribution is

If the heights of 99.7% of American men are between 5'0" and 7'0", what is your estimate of the standard deviation of the height of American men? Assume the heights of American men are approximately Normally distributed.

A student is told that her score on an exam is at the 50th percentile of the distribution of scores. This means that:

A study of grades at a large university finds that the mean GPA for all undergraduates is 2.77. The distribution of grades is roughly normal. To make this description useful we must also know

The distribution of the number of dill pickle spears in a gallon container is approximately Normal with mean 110 and standard deviation 10. Approximately what percent of the containers had between 90 and 130 spears?