ECN 221 Exam 2 Question and answers
already passed 2025
As the sample size increases, the variability among the sample means -
correct answer ✔decreases
The area of the continuous uniform probability distribution is - correct answer
✔rectangular
The random variable x is the number of occurrences of an event over an
interval of ten minutes. It can be assumed that the probability of an
occurrence is the same in any two time periods of an equal length. It is known
that the mean number of occurrences in ten minutes is 5.3. The expected
value of the random variable x is - correct answer ✔5.3
A sample of 2500 people was asked how many cups of coffee they drink in
the morning. You are given the following sample information.
Cups of coffee: 0, 1, 2, 3,
Frequency: 700, 900, 500, 400 = 2500
The expected number of cups of coffee is - correct answer ✔1.24
The time it takes to travel from home to the office is normally distributed with
u=25 minutes and o=5 minutes. What is the probability the trip takes between
20 and 30 minutes? - correct answer ✔0.6826
, The sample size needed to provide a margin of error of 3 or less with a .95
probability when the population standard deviation equals 11 is - correct
answer ✔52
From a population that is not normally distributed and whose standard
deviation is not known, a sample of 50 items is selected to develop an interval
estimate for u. Which of the following statements is true?
-The sample size must be increased in order to develop an interval estimate
-The t distribution with 49 degrees of freedom must be used
-The standard normal distribution can be used
-The t distribution with 50 degrees of freedom must be used - correct answer
✔The t distribution with 49 degrees of freedom must be used.
x is normally distributed random variable with a mean of 24 and a standard
deviation of 6. The probability that x is less than 11.5 is - correct answer
✔0.0186
A population has a standard deviation of 16. If a sample of size 64 is selected
from this population, that is the probability that the sample mean will be within
+-2 of the population mean? - correct answer ✔0.6826
In order to estimate the average time spent per student on the computer
terminals at a local university, data were collected for a sample of 64 business
students over a one-week period. Assume the population standard deviation
is 1.6 hours. If the sample mean is 9 hours, then the 95% confidence interval
is _______ hours. - correct answer ✔8.608 to 9.392
A professor at a local university noted that the exam grades of her students
were normally distributed with a mean of 73 and a standard deviation of 11.
The professor has informed us that 8.75 percent of her students received
already passed 2025
As the sample size increases, the variability among the sample means -
correct answer ✔decreases
The area of the continuous uniform probability distribution is - correct answer
✔rectangular
The random variable x is the number of occurrences of an event over an
interval of ten minutes. It can be assumed that the probability of an
occurrence is the same in any two time periods of an equal length. It is known
that the mean number of occurrences in ten minutes is 5.3. The expected
value of the random variable x is - correct answer ✔5.3
A sample of 2500 people was asked how many cups of coffee they drink in
the morning. You are given the following sample information.
Cups of coffee: 0, 1, 2, 3,
Frequency: 700, 900, 500, 400 = 2500
The expected number of cups of coffee is - correct answer ✔1.24
The time it takes to travel from home to the office is normally distributed with
u=25 minutes and o=5 minutes. What is the probability the trip takes between
20 and 30 minutes? - correct answer ✔0.6826
, The sample size needed to provide a margin of error of 3 or less with a .95
probability when the population standard deviation equals 11 is - correct
answer ✔52
From a population that is not normally distributed and whose standard
deviation is not known, a sample of 50 items is selected to develop an interval
estimate for u. Which of the following statements is true?
-The sample size must be increased in order to develop an interval estimate
-The t distribution with 49 degrees of freedom must be used
-The standard normal distribution can be used
-The t distribution with 50 degrees of freedom must be used - correct answer
✔The t distribution with 49 degrees of freedom must be used.
x is normally distributed random variable with a mean of 24 and a standard
deviation of 6. The probability that x is less than 11.5 is - correct answer
✔0.0186
A population has a standard deviation of 16. If a sample of size 64 is selected
from this population, that is the probability that the sample mean will be within
+-2 of the population mean? - correct answer ✔0.6826
In order to estimate the average time spent per student on the computer
terminals at a local university, data were collected for a sample of 64 business
students over a one-week period. Assume the population standard deviation
is 1.6 hours. If the sample mean is 9 hours, then the 95% confidence interval
is _______ hours. - correct answer ✔8.608 to 9.392
A professor at a local university noted that the exam grades of her students
were normally distributed with a mean of 73 and a standard deviation of 11.
The professor has informed us that 8.75 percent of her students received
