Exam 2 (1/3)

Birth weights of full-term babies in a certain area are normally distributed with mean 7.13 pounds and standard deviation 1.29 pounds. Calculate the z-score for a full-term newborn weighing 5.324 pounds. Do not round.

-1.4

Pregnancy length (in days) is a normally distributed random variable with a mean of 266 days and a standard deviation of 16 days. Births that occur before 245 days are considered premature. What is the probability that a randomly selected newborn baby is premature? Use the appropriate applet. Enter a number in decimal form, e.g. 0.68 not 68 or 68%.

0.0946

Light bulbs used for the exterior walkways of a college campus have an average lifetime of 500 hours. Assume that the lifetime of bulbs is normally distributed with standard deviation 50 hours. Suppose all of the bulbs were replaced at the same time and they have been turned on for a total of 550 hours. What is the probability that a randomly chosen light bulb lasts less than 550 hours?

0.84

A plant biologist studies the height of sunflowers. He measures a large sample of sunflowers and creates a probability distribution. The distribution is normal in shape with mean 112 cm and standard deviation 16 cm. What is the probability (approximately) that a sunflower will be less than 136 cm tall?

0.93

The incubation period for the eggs of a House Wren has a normal probability distribution with a mean time of 336 hours and a standard deviation of 3.5 hours. Before hatching, a particular House Wren egg incubated for 343 hours. What is the probability that House Wren eggs will take longer than 343 hours to hatch?

2.5%

In Ms. Polakoski's statistics class the mean score on the final exam is 78 points with a standard deviation of 8 points. Carl was enrolled in Ms. Polakoski's class. His score on the final exam was 89.2. In Mr. Curtis' statistics class the mean score on the final exam is 82 points with a standard deviation of 4 points. Ray was enrolled in Mr. Curtis' class. His score on the final exam was 87.6. Who performed better on the final exam relative to their classmates?

Relative to their classmates, neither performed better on the final exam relative to his classmates. Compare z scores Carl's z-score is:z=(89.2−78)/8=1.4 Ray's z-score is: z=(87.6−82)/4=1.4

QUESTION ON OTHER SIDE: μ=(7+13)/2=(20)/2=10 3

Use the normal curve below and the empirical rule to find the the standard deviation for the height data. Enter only a number (no words or symbols), and do not round.

Which of the following is the appropriate interpretation for when an event has a probability of 1? -We are absolutely certain that the event will occur. -The event will never occur. -The relative frequency will be more than 1.

We are absolutely certain that the event will occur.

In a survey of men in the United States (ages 20 to 29), the mean height was 69.9 inches with a standard deviation of 3.0 inches. Assume the height data is normally distributed. Zak's height has a z-score of -1.7. Which one of the following statements is true? -Zak is shorter than 65 inches. -Zak's height is in the lower 2.5% of men's heights (ages 20 to 29). -Zak is taller than 72.9 inches.

Zak is shorter than 65 inches.

Which of the following is a discrete quantitative variable for a randomly selected person in the U.S.? - weight - blood type - number of pets owned

number of pets owned