MATH 120 EXAMS 2025/26 QUESTIONS WITH COMPLETE SOLUTIONS.
What is the impact of changing from the 90% confidence interval to the 99% confidence interval? -
(ANSWER)The range of values included increases.
What does decreasing the standard deviation of the sample do to the confidence interval? -
(ANSWER)The range of values included decreases.
What is the impact of decreasing the sample size? - (ANSWER)The range of values included increases.
Which accurately describes widening the range of the confidence interval (by changing the confidence
level)? - (ANSWER)The range is wider so the certainty is higher.
A delivery company provides expected time of arrival. The company wants to provide an accurate
suggestion with a 90% confidence level. If the sample size is 50, the sample average is 35 minutes, the
standard deviation is 10 minutes, and the z-score is 1.65, what is the standard error of the mean? -
(ANSWER)1.41
A delivery company provides expected time of arrival. The company wants to provide an accurate
suggestion with a 90% confidence level. If the sample size is 50, the sample average is 35 minutes, the
standard deviation is 10 minutes, and the z-score is 1.65, what is the margin of error? - (ANSWER)2.33
A delivery company provides expected time of arrival. The company wants to provide an accurate
suggestion with a 90% confidence level. If the sample size is 50, the sample average is 35 minutes, the
standard deviation is 10 minutes, and the z-score is 1.65, what is the confidence interval? -
(ANSWER)(32.67, 37.33)
A pharmaceutical company is launching a new medication intended to treat epilepsy. Which of the
following would make sense as a null hypothesis when testing the efficacy of the drug? - (ANSWER)Ho:
The drug is not an effective treatment for epilepsy.
A pharmaceutical company is launching a new medication intended to treat epilepsy. The company
performs a study that maintains the null hypothesis. What is the finding of the company? -
(ANSWER)The evidence suggests that the drug is not an effective treatment against epilepsy.
1
, MATH 120 EXAMS 2025/26 QUESTIONS WITH COMPLETE SOLUTIONS.
A supplier of parts to the automobile industry is launching a new brake pad intended to wear down
more slowly while delivering the same performance. The company performs a study that incorrectly
rejects the null hypothesis. What type of error is this? - (ANSWER)Type 1: The supplier rejected the null
when it should not have.
A supplier of parts to the automobile industry is launching a new brake pad intended to wear down
more slowly while delivering the same performance. The company performs a study that incorrectly
maintains the null hypothesis. What type of error is this? - (ANSWER)Type 2: The supplier maintained
the null when it should have rejected it.
When assessing the significance of a study, we're asking: - (ANSWER)What is the likelihood that we
incorrectly reject the null?
You're surprised to learn that instead of ~$100, a 0.30 carat costs ~$800 carats. Which explanation
would make sense? - (ANSWER)The linear regression is not accurate at predicting the cost of diamonds
below 0.40 carats.
There is a fixed cost associated with procuring the diamond and offering it for sale, meaning that small
diamonds have a relatively high price.
The diamond is very high quality as measured by other metrics (e.g., cut, clarity, color).
**All of the above.**
If a residual is negative, what does it mean about the observed value? - (ANSWER)The predicted value is
greater than the observed value.
If the expected value of a diamond is $3,500, but the observed value is $3,800, what is the residual? -
(ANSWER)$300
If the correlation between the price of two stocks is 0.83, what does this indicate? - (ANSWER)Strong
positive correlation
2
What is the impact of changing from the 90% confidence interval to the 99% confidence interval? -
(ANSWER)The range of values included increases.
What does decreasing the standard deviation of the sample do to the confidence interval? -
(ANSWER)The range of values included decreases.
What is the impact of decreasing the sample size? - (ANSWER)The range of values included increases.
Which accurately describes widening the range of the confidence interval (by changing the confidence
level)? - (ANSWER)The range is wider so the certainty is higher.
A delivery company provides expected time of arrival. The company wants to provide an accurate
suggestion with a 90% confidence level. If the sample size is 50, the sample average is 35 minutes, the
standard deviation is 10 minutes, and the z-score is 1.65, what is the standard error of the mean? -
(ANSWER)1.41
A delivery company provides expected time of arrival. The company wants to provide an accurate
suggestion with a 90% confidence level. If the sample size is 50, the sample average is 35 minutes, the
standard deviation is 10 minutes, and the z-score is 1.65, what is the margin of error? - (ANSWER)2.33
A delivery company provides expected time of arrival. The company wants to provide an accurate
suggestion with a 90% confidence level. If the sample size is 50, the sample average is 35 minutes, the
standard deviation is 10 minutes, and the z-score is 1.65, what is the confidence interval? -
(ANSWER)(32.67, 37.33)
A pharmaceutical company is launching a new medication intended to treat epilepsy. Which of the
following would make sense as a null hypothesis when testing the efficacy of the drug? - (ANSWER)Ho:
The drug is not an effective treatment for epilepsy.
A pharmaceutical company is launching a new medication intended to treat epilepsy. The company
performs a study that maintains the null hypothesis. What is the finding of the company? -
(ANSWER)The evidence suggests that the drug is not an effective treatment against epilepsy.
1
, MATH 120 EXAMS 2025/26 QUESTIONS WITH COMPLETE SOLUTIONS.
A supplier of parts to the automobile industry is launching a new brake pad intended to wear down
more slowly while delivering the same performance. The company performs a study that incorrectly
rejects the null hypothesis. What type of error is this? - (ANSWER)Type 1: The supplier rejected the null
when it should not have.
A supplier of parts to the automobile industry is launching a new brake pad intended to wear down
more slowly while delivering the same performance. The company performs a study that incorrectly
maintains the null hypothesis. What type of error is this? - (ANSWER)Type 2: The supplier maintained
the null when it should have rejected it.
When assessing the significance of a study, we're asking: - (ANSWER)What is the likelihood that we
incorrectly reject the null?
You're surprised to learn that instead of ~$100, a 0.30 carat costs ~$800 carats. Which explanation
would make sense? - (ANSWER)The linear regression is not accurate at predicting the cost of diamonds
below 0.40 carats.
There is a fixed cost associated with procuring the diamond and offering it for sale, meaning that small
diamonds have a relatively high price.
The diamond is very high quality as measured by other metrics (e.g., cut, clarity, color).
**All of the above.**
If a residual is negative, what does it mean about the observed value? - (ANSWER)The predicted value is
greater than the observed value.
If the expected value of a diamond is $3,500, but the observed value is $3,800, what is the residual? -
(ANSWER)$300
If the correlation between the price of two stocks is 0.83, what does this indicate? - (ANSWER)Strong
positive correlation
2
