CSUF ISDS 361A PRACTICE EXAM 2
VERSION B SKORDI COMPLETE
QUESTIONS AND CORRECT ANSWERS
LATEST UPDATE 2025/2026 GRADED A+ .
,1. The following 5 questions are based on this information.
Suppose a random sample of 18 uber drivers was taken, and the average age X¯ of these drivers was found to be
27.5 years. Construct a 99% confidence interval for the mean age (µ) of all drivers.
Assume that the age of drivers is normally distributed with a population stan- dard deviation (σ) of 2.3 years. ✔✔ correc
answer You need to know this for the next five questions
2. The standard error (SE) of X¯ is Select one ✔
✔ correct answer
a. 0.13
b. 6.48
c. 2.3
d. 0.54 ✔✔ correct answer SE= sigma/sqrt (n)
n 18
mean 27.5
sigma 2.3
d. 0.54
3. The critical value (CV) used for a 99% interval estimate is Select one ✔✔ correct
answer
a. 2.58
b. 2.32
c. 0.01
d. 0.005 ✔✔ correct answer CV = -NORM.S.INV(0.01/2)
a. 2.58
4. The 99% confidence interval estimate of µ is Select one ✔✔
correct answer
,a. 27.5 ± 0.54
b. 27.5 ± 1.26
c. 27.5 ± 2.3
d. 27.5 ± 1.39 ✔✔ correct answer Interval Estinate = Point estimate +/- ME. ME
= CV * SE
PE = 27.5
ME =1.39
d. 27.5 ± 1.39
5. The company claims that average age of drivers is 26.9 years. In light of the sample evidence and at the 1%
level of significance,
Select one ✔✔ correct answer
a. Your claim is statistically justified
b. Your claim is not statistically justified ✔✔ correct answer 26.5 falls in the range 27.5 +/- 1.39. Hence, the claim is statistically justified
a. Your claim is statistically justified
6. If we decrease the confidence level (1-α) from 0.99 to 0.95, the margin of error (ME) of the confidence interval
estimate will
Select one ✔✔ correct answer
a. be zero
b. increase
c. stays the same
d. decrease ✔✔ correct answer ME is decreases with decrease in the confidence level.
d. decrease
7. The following 6 questions are based on this information.
, A large cycle company reported that in 2010, 65% of parents of children (be- tween the ages of 8 to 12), bought
their children a cycle.
That same company has stated that cycle purchases for that same age group have gone up. They surveyed 300
parents of children and found that 230 of them have bought cycle to their children. ✔✔ correct answer you will need to know
these for the six questions
VERSION B SKORDI COMPLETE
QUESTIONS AND CORRECT ANSWERS
LATEST UPDATE 2025/2026 GRADED A+ .
,1. The following 5 questions are based on this information.
Suppose a random sample of 18 uber drivers was taken, and the average age X¯ of these drivers was found to be
27.5 years. Construct a 99% confidence interval for the mean age (µ) of all drivers.
Assume that the age of drivers is normally distributed with a population stan- dard deviation (σ) of 2.3 years. ✔✔ correc
answer You need to know this for the next five questions
2. The standard error (SE) of X¯ is Select one ✔
✔ correct answer
a. 0.13
b. 6.48
c. 2.3
d. 0.54 ✔✔ correct answer SE= sigma/sqrt (n)
n 18
mean 27.5
sigma 2.3
d. 0.54
3. The critical value (CV) used for a 99% interval estimate is Select one ✔✔ correct
answer
a. 2.58
b. 2.32
c. 0.01
d. 0.005 ✔✔ correct answer CV = -NORM.S.INV(0.01/2)
a. 2.58
4. The 99% confidence interval estimate of µ is Select one ✔✔
correct answer
,a. 27.5 ± 0.54
b. 27.5 ± 1.26
c. 27.5 ± 2.3
d. 27.5 ± 1.39 ✔✔ correct answer Interval Estinate = Point estimate +/- ME. ME
= CV * SE
PE = 27.5
ME =1.39
d. 27.5 ± 1.39
5. The company claims that average age of drivers is 26.9 years. In light of the sample evidence and at the 1%
level of significance,
Select one ✔✔ correct answer
a. Your claim is statistically justified
b. Your claim is not statistically justified ✔✔ correct answer 26.5 falls in the range 27.5 +/- 1.39. Hence, the claim is statistically justified
a. Your claim is statistically justified
6. If we decrease the confidence level (1-α) from 0.99 to 0.95, the margin of error (ME) of the confidence interval
estimate will
Select one ✔✔ correct answer
a. be zero
b. increase
c. stays the same
d. decrease ✔✔ correct answer ME is decreases with decrease in the confidence level.
d. decrease
7. The following 6 questions are based on this information.
, A large cycle company reported that in 2010, 65% of parents of children (be- tween the ages of 8 to 12), bought
their children a cycle.
That same company has stated that cycle purchases for that same age group have gone up. They surveyed 300
parents of children and found that 230 of them have bought cycle to their children. ✔✔ correct answer you will need to know
these for the six questions
