6. Suppose that the lifespan of a laptop battery is normally distributed with a mean of 2500 hours and a standard deviation of 60 hours. What is the probability that a randomly chosen battery will...

6. Suppose that the lifespan of a laptop battery is normally distributed with a mean of 2500 hours
and a standard deviation of 60 hours. What is the probability that a randomly chosen battery
will last at most 2560 hours?
a. 0.1587
b. 0.8413
c. 0.6539
d. 0.3461

7. A random sample of 123 college professors were surveyed to determine the proportion who
owned a pet. 86 reported owning pets. Construct a 98% confidence interval for the true
population proportion of college professors who own a pet.
a. (0.6181, 0.7802)
b. (0.6030, 0.7954)
c. (0.6312, 0.7672)
d. (0.5927, 0.8057)