MATH 120 EXAMS QUESTIONS WITH VERIFIED
ANSWERS
What is the impact of changing from the 90% confidence interval to the 99% confidence
interval? - Answers - The range of values included increases.
What does decreasing the standard deviation of the sample do to the confidence
interval? - Answers - The range of values included decreases.
What is the impact of decreasing the sample size? - Answers - The range of values
included increases.
Which accurately describes widening the range of the confidence interval (by changing
the confidence level)? - Answers - 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? - Answers - 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? - Answers - 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? - Answers - (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? - Answers - 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? - Answers - The evidence suggests that the drug is not an effective
treatment against epilepsy.
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? - Answers
- 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? -
Answers - Type 2: The supplier maintained the null when it should have rejected it.
When assessing the significance of a study, we're asking: - Answers - 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? - Answers - 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? - Answers - 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? - Answers - $300
If the correlation between the price of two stocks is 0.83, what does this indicate? -
Answers - Strong positive correlation
If the coefficient of determination between the price of a house and it square footage is
65%, what percentage of the variation in the price of the house is explained by its size?
- Answers - 65%
If the correlation coefficient between the price of a car and its mileage is 60%, what
percentage of the price of the car is explained by its mileage? - Answers - 36%
If the regression line comparing the age of a used car to its price has the equation c = -
3000a + 36000, what is the expected cost of an 8-year-old car? - Answers - $12,000
If the regression line comparing the age of a used car to its price has the equation c = -
3000a + 36000 and the residual is $3,000, what is the observed cost of an 8-year-old
car? - Answers - $15,000
If the regression line comparing the age of a used car to its price has the equation c = -
3000a + 36000, what is the expected age of a car that costs $27,000? - Answers - 3
years
If the r-squared of the regression line comparing the age of a used motorcycle to its cost
is 64%, what is the correlation coefficient? - Answers - -0.80
ANSWERS
What is the impact of changing from the 90% confidence interval to the 99% confidence
interval? - Answers - The range of values included increases.
What does decreasing the standard deviation of the sample do to the confidence
interval? - Answers - The range of values included decreases.
What is the impact of decreasing the sample size? - Answers - The range of values
included increases.
Which accurately describes widening the range of the confidence interval (by changing
the confidence level)? - Answers - 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? - Answers - 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? - Answers - 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? - Answers - (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? - Answers - 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? - Answers - The evidence suggests that the drug is not an effective
treatment against epilepsy.
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? - Answers
- 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? -
Answers - Type 2: The supplier maintained the null when it should have rejected it.
When assessing the significance of a study, we're asking: - Answers - 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? - Answers - 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? - Answers - 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? - Answers - $300
If the correlation between the price of two stocks is 0.83, what does this indicate? -
Answers - Strong positive correlation
If the coefficient of determination between the price of a house and it square footage is
65%, what percentage of the variation in the price of the house is explained by its size?
- Answers - 65%
If the correlation coefficient between the price of a car and its mileage is 60%, what
percentage of the price of the car is explained by its mileage? - Answers - 36%
If the regression line comparing the age of a used car to its price has the equation c = -
3000a + 36000, what is the expected cost of an 8-year-old car? - Answers - $12,000
If the regression line comparing the age of a used car to its price has the equation c = -
3000a + 36000 and the residual is $3,000, what is the observed cost of an 8-year-old
car? - Answers - $15,000
If the regression line comparing the age of a used car to its price has the equation c = -
3000a + 36000, what is the expected age of a car that costs $27,000? - Answers - 3
years
If the r-squared of the regression line comparing the age of a used motorcycle to its cost
is 64%, what is the correlation coefficient? - Answers - -0.80
