## Question

###### 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.