CSUF ISDS 361A Practice Exam 2 Version B Skordi
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. - -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 - -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 - -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 - -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 - -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 - -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. - -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 - -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
Select one:
a. 0.037
b. 0.024
c. 0.047
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. - -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 - -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 - -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 - -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 - -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 - -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. - -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 - -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
Select one:
a. 0.037
b. 0.024
c. 0.047
