Statistical methods in economics and business
Given that X is a normally distributed random variable with a mean of 50 and a standard deviation of 2, the probability that X is between 48 and 52 is
a) Approximately 68%
b) Approximately 95%
c) Approximately 99%
d) Can’t tell without the z-table.
2. A lab orders 100 rats a week for each of the 52 weeks in the year for experiments that the lab conducts. Suppose the mean cost of rats used in lab experiments turned out to be $13.00 per week. Interpret this value.
a) Most of the weeks resulted in rat costs of $13.00.
b) The median cost for the distribution of rat costs is $13.00.
c) The expected or average cost for all weekly rat purchases is $13.00.
d) The rat cost that occurs more often than any other is $13.00.
3. Which of the following about the normal distribution is NOT true?
a) Theoretically, the mean, median, and mode are the same.
b) About 2/3 of the observations fall within 1 standard deviation from the mean.
c) It is a discrete probability distribution.
d) Its parameters are the mean, μ, and standard deviation, σ.
4. Suppose a standard normal distributed random variable z turned out to has a value of .75, this means that
a) 25% of the time this random variable is greater than .75.
b) 22.7% of the time this random variable is greater than .75.
c) 75% of the time this random variable is greater than .75.
d) None of the above is true.