CSUF ISDS 361A PRACTICE EXAM
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 standard deviation (σ) of 2.3
years. – correct answer✔✔ You need to know this for the next five questions
The standard error (SE) of X¯ is
Select one:
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
The critical value (CV) used for a 99% interval estimate is
Select one:
a. 2.58
b. 2.32
c. 0.01
d. 0.005 – correct answer✔✔ CV = -NORM.S.INV(0.01/2)
a. 2.58
The 99% confidence interval estimate of µ is
Select one:
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
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:
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
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:
a. be zero
b. increase
c. stays the same
d. decrease – correct answer✔✔ ME is decreases with decrease in the confidence level.
d. decrease
The following 6 questions are based on this information.
A large cycle company reported that in 2010, 65% of parents of children (between 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
Specify the null and alternative hypotheses.
Select one:
a. H(0): p≥0.65 Versus H(a): p<0.65 b. H(0): p≤0.65 Versus H(a): p>0.65 – correct answer✔✔ That same company has stated that cell phone
purchases for that same age group have gone up.
Hence, H(0): p≤0.65 Versus H(a): p>0.65
b. H(0): p≤0.65 Versus H(a): p>0.65
The standard error (SE) of p¯ is
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For reference https://business.fullerton.edu/academics/isds/courses