PSY 230 Final Exam Study Guide
UPDATED ACTUAL Exam Questions and
CORRECT Answers
What is the critical Z value for an 80% confidence interval? - CORRECT ANSWER -1
What is the critical Z value for a 90% confidence interval? - CORRECT ANSWER -1
What is the critical Z value for a 95% confidence interval? - CORRECT ANSWER -1
What is the critical Z value for a 99% confidence interval? - CORRECT ANSWER -2
How does confidence level affect the width of a confidence interval? - CORRECT
ANSWER -A higher confidence level results in a wider confidence interval.
Which factors impact the margin of error of a confidence interval about the mean? - CORRECT
ANSWER -Sample size, confidence level, and standard deviation.
How do you compute the 90% confidence interval for the proportion of heads observed when
flipping a coin 100 times with 65 heads? - CORRECT ANSWER -The 90% confidence
interval is approximately (0.65 - 0.086, 0.65 + 0.086) or (0.564, 0.736).
How do you compute the 95% confidence interval for the proportion of people who enjoyed the
new park from a survey of 75 people, 60 of whom enjoyed it? - CORRECT ANSWER -
The 95% confidence interval is approximately (0.60 - 0.085, 0.60 + 0.085) or (0.515, 0.685).
How do you compute the 95% confidence interval for the mean weight of cereal bags if the
sample mean is 77 ounces and the standard deviation is 7 ounces from 36 bags? - CORRECT
ANSWER -The 95% confidence interval is approximately (77 - 2.1, 77 + 2.1) or (74.9,
79.1) ounces.
, How do you compute the 90% confidence interval for the mean recovery time of a medical
procedure with a mean of 46.3 days and a standard deviation of 12 days from 100 people? -
CORRECT ANSWER -The 90% confidence interval is approximately (46.3 - 1.645*1.2,
46.3 + 1.645*1.2) or (44.6, 48.0) days.
What is the minimum sample size required for a 95% confidence interval with a margin of error
of 5 and a population standard deviation of 10? - CORRECT ANSWER -The minimum
sample size required is 384.
What is the minimum sample size required for a 90% confidence interval with a margin of error
of 2 and a population standard deviation of 5? - CORRECT ANSWER -The minimum
sample size required is 86.
What is the minimum sample size required for a 99% confidence interval with a margin of error
of 10 and a population standard deviation of 25? - CORRECT ANSWER -The minimum
sample size required is 97.
What does a confidence interval tell us? - CORRECT ANSWER -It provides a range of
values within which we expect the population parameter to lie.
What does a confidence interval not tell us? - CORRECT ANSWER -It does not provide
the exact value of the population parameter.
What conclusions can we make from a hypothesis test? - CORRECT ANSWER -We can
either reject or fail to reject the null hypothesis based on the evidence.
What is the null hypothesis in a left-tailed hypothesis test for the mean? - CORRECT
ANSWER -H0: μ ≥ μ0.
What is the null hypothesis in a right-tailed hypothesis test for the mean? - CORRECT
ANSWER -H0: μ ≤ μ0.
UPDATED ACTUAL Exam Questions and
CORRECT Answers
What is the critical Z value for an 80% confidence interval? - CORRECT ANSWER -1
What is the critical Z value for a 90% confidence interval? - CORRECT ANSWER -1
What is the critical Z value for a 95% confidence interval? - CORRECT ANSWER -1
What is the critical Z value for a 99% confidence interval? - CORRECT ANSWER -2
How does confidence level affect the width of a confidence interval? - CORRECT
ANSWER -A higher confidence level results in a wider confidence interval.
Which factors impact the margin of error of a confidence interval about the mean? - CORRECT
ANSWER -Sample size, confidence level, and standard deviation.
How do you compute the 90% confidence interval for the proportion of heads observed when
flipping a coin 100 times with 65 heads? - CORRECT ANSWER -The 90% confidence
interval is approximately (0.65 - 0.086, 0.65 + 0.086) or (0.564, 0.736).
How do you compute the 95% confidence interval for the proportion of people who enjoyed the
new park from a survey of 75 people, 60 of whom enjoyed it? - CORRECT ANSWER -
The 95% confidence interval is approximately (0.60 - 0.085, 0.60 + 0.085) or (0.515, 0.685).
How do you compute the 95% confidence interval for the mean weight of cereal bags if the
sample mean is 77 ounces and the standard deviation is 7 ounces from 36 bags? - CORRECT
ANSWER -The 95% confidence interval is approximately (77 - 2.1, 77 + 2.1) or (74.9,
79.1) ounces.
, How do you compute the 90% confidence interval for the mean recovery time of a medical
procedure with a mean of 46.3 days and a standard deviation of 12 days from 100 people? -
CORRECT ANSWER -The 90% confidence interval is approximately (46.3 - 1.645*1.2,
46.3 + 1.645*1.2) or (44.6, 48.0) days.
What is the minimum sample size required for a 95% confidence interval with a margin of error
of 5 and a population standard deviation of 10? - CORRECT ANSWER -The minimum
sample size required is 384.
What is the minimum sample size required for a 90% confidence interval with a margin of error
of 2 and a population standard deviation of 5? - CORRECT ANSWER -The minimum
sample size required is 86.
What is the minimum sample size required for a 99% confidence interval with a margin of error
of 10 and a population standard deviation of 25? - CORRECT ANSWER -The minimum
sample size required is 97.
What does a confidence interval tell us? - CORRECT ANSWER -It provides a range of
values within which we expect the population parameter to lie.
What does a confidence interval not tell us? - CORRECT ANSWER -It does not provide
the exact value of the population parameter.
What conclusions can we make from a hypothesis test? - CORRECT ANSWER -We can
either reject or fail to reject the null hypothesis based on the evidence.
What is the null hypothesis in a left-tailed hypothesis test for the mean? - CORRECT
ANSWER -H0: μ ≥ μ0.
What is the null hypothesis in a right-tailed hypothesis test for the mean? - CORRECT
ANSWER -H0: μ ≤ μ0.
