Algebra 2 DLD 18 - Normal Distribution

2000 freshman at NC State University took a biology test. The scores were distributed normally with a mean of 70 and a standard deviation of 5. What percentage of scores are between 65 and 75?

• 34%

• 50%

• 68%

• 99%

500 juniors at Central High School took the ACT last year. The scores were distributed normally with a mean of 24 and standard deviation of 4. Approximately how many juniors scored between 24 and 28?

• 170

• 250

• 340

• 180

The number of nails of a given length is normally distributed with a mean length of 5 inches and standard deviation of 0.03 inches. Find the number of nails in a bag of 120 that are less than 4.97 inches long.

• 16

• 19

• 50

• 60

The actual weights of bags of pet food are normally distributed. The mean of weights is 50 lb. with a standard deviation of 0.2 lb. In a group of 250 bags, how many would you expect to weigh more than 50.4 lb.

• 16

• 40

• 2.5

• 6.25

A test was given to 120 students, and the score approimated a normal distribution. If the mean score was 72 with a standard deviation of 7, approximately how many students had scores higher than 65?

• 79

• 87

• 101

• 98

A machine is used to put bolts into boxes. It does so such that the actual number of bolts in a box is normally distributed with a mean of 106 and a standard deviation of 2. What is the probability of selecting a box that contains less than 108 bolts?

• 0.84

• 84

• 0.64

• 64

The heights of people on planet Ixx are normally distributed with a mean of 40 inches and a standard devation of 5 inches. [They are vertically diverse] 16% of Ixxians are over ______ inches tall?

• 30

• 35

• 40

• 45

Battery lifetime is normally distributed for large samples. The mean lifetime is 500 days and the standard deviation is 61 days. Approximately what percet of batteries have lifetimes longer than 622 days?

• 18.5%

• 16%

• 2.5%

• 34%

The heights of the female students in J.K. High School are normally distruted with a mean of 66 inches. If 95% of the heights of these students fell between 63 and 69 inches, what is the standard deviation for this set of data?

• 66

• 6

• 3

• 1.5

The average weight of men in America is 180 pounds with a standard deviation of 25 pounds. The weights are approximately normally distributed. What percent of men havea weight less than 105 pounds?

• 2.5

• 13.5

• 0.15

• 16