Random samples of size 81 are taken from a process (an infinite population) whose mean and standard deviation are 200 and 18, respectively. The distribution of the population is unknown. The mean and the standard error of the distribution of sample means are _____.
a. 200 and 18
b. 81 and 18
c. 9 and 2
d. 200 and 2
Question 2
The average number of calls received by a switchboard in a 30-minute period is 15.
a. Define the random variable in words for this experiment.
b. What is the probability that between 10:00 and 10:30 the switchboard will receive exactly 10 calls?
c. What is the probability that between 10:00 and 10:30 the switchboard will receive more than 9 calls but fewer than 15 calls?
d. What is the probability that between 10:00 and 10:30 the switchboard will receive fewer than 7 calls?
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