Elementary Statistics Formative Guide 3
1) Which does not describe the Standard Normal Distribution.
a) probability of any single value is zero
b) standard deviation > 1
c) continuous probability distribution
d) symmetric
2) Approximately what percent of scores fall within one standard deviation above the mean under the
normal curve? (from the middle to 1 standard deviation above the middle)
a) 34%
b) 95%
c) 68%
d) 50%
3) Find the area under a normal probability curve between Z-values of -.4 and 1.43.
a) .579
b) .1554
c) .3643
d) .4236
4) Standardize a scored of 55 if the mean and standard deviation of its sample is 74 and 14.
a) -19
b) 1.36
c) - 1.36
d) 5.29
5) According to Nielsen Media Research, people watch television an average of 6.98 hours per day.
Assume that these times are normally distributed with a standard deviation of 3.8 hours. Find the
probability that a randomly selected person watched television more than 5 hours in a day.
a) .7947
b) .1985
c) .6985
d) .213
6) The weights of women aged 18 to 24 are normally distributed with a mean of 132 lb and a standard
deviation of 27.4 lb. Find the probability that a randomly selected women from the 18 to 24 age
range weighs between 110 and 125 lbs?
a) .29
b) .19
c) .10
d) .71
7) On the Graduate Record Exam in mathematics, scores are normally distributed with a mean of 600
and a standard deviation of 115. If a college admissions office decides to require scores above the
75th percentile, find the cut-off score.
a) 615
b) 75
c) 749
d) 678
8) A machine fills sugar boxes in such a way that the weights of the content are normally distributed
with a mean of 2260 and a standard deviation of 20. Another machine checks the packages and
rejects the top and bottom 5%. Find the minimum and maximum acceptable weights.
a) 2213 - 2306
b) 1834 - 2533
c) 2227 - 2293
d) 2000 - 2300
9) Find the mean and standard deviation of a binomial distribution given a sample size of 400 and a
sample proportion of p = .15.
a) 60, 51
b) 400, 15
c) .15, 51
d) 51,60
e) 60, 7.14
10) Among U. S. households, 24% have telephone answering machines. If a telemarketing campaign
involves 2000 households, find the probability that 500 or more have answering machines.
a) .5
b) .24
c) .01
d) .36
e) .14
11) College freshman study each week an average of 7 hours with a standard deviation of
3.52 hours. If 90 freshman are randomly selected, find the probability that their mean
weekly study time exceeds 8 hours.
a) .5
b) .404
c) .15
d) .0170
e) .0036
1
Elementary Statistics Formative Guide 3
12) The National Center for Educational Statistics surveyed 4400 college graduates about the lengths
of time required to earn their bachelors degrees. The mean is 5.15 years and the standard
deviation is 1.68 years. Based on this sample, construct a 90% confidence interval for the mean
time required by all college graduates
a) 5.08-5.22
b) 5.1 - 5.19
c) 4.01-6.39
d) 4.37-6.06
13)Which statistic would be more informative about gas mileage for a single person buying a new car?
a) point estimate
b) interval estimate c) confidence interval
d) sampling distribution
14) What is the degrees of freedom given a sample size of 22?
a) 22
b) 23
c) 21
d) 20
15) Given a sample standard deviation of 50 and a sample size of 20, calculate the standard error of
the mean.
a) 11.18
b) 2.5
c) 50
d) 20
16) What is the most conservative probability of success when creating confidence intervals about a
sample proportion.
a) .5
b) .1
c) .9
d) changes with sample size
17) Create a 99% confidence interval about the sample proportion given that the proportion is .42 and
the sample size is 500.
a) .42
b) .0568
c) .36 - .477
d) .4 - .44
18) Find the sample size needed to stay within 2 units of the sample mean given the sample standard
deviation is 12 and you are going to create a 90% confidence interval.
a) 98
b) 49
c) 9.87
d) 24
19) The t-distribution is used when the sample size is less than ___________.
20) The theorem considered to be the most important in statistics is ____________.
21) A range of values likely to contain the population parameter is a ___________.
22) A density curve has all positive values and the total area under the curve is equal to _________
2