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Review #1
January 13, 2016
The Woodcock Johnson Cognitive Scale results in a normal distribution
with a mean of 110 and a standard deviation of 25. If someone tests at
the 80th percentile, what score did that individual have?
(a) 89
(b) 113
(c) 118
(d) 130
(e) 131
For the standard normal curve, find the z-score that corresponds to the
83rd percentile.
Given a mean of 24, standard deviation of 2.8, and Z-score of 1.8, find the
value of x, the data point.
(a) -18.96
(b) 27.03
(c) -4.08
(d) 23
(e) 29.04
Choose the answer below that identifies a value for y that results in a valid
probability distribution.
y = 0.20
y = 0.15
y = -.25
y = 1.85
y = 0.65
5. When using a random number table to get a list of nine random numbers
from 587 to 6340, you would use groups of
(a) 7 digits.
(b) 2 digits.
(c) 4 digit.
(d) 3 digits.
(e) 3 digits and then 4 digits.
6. Given that x is a normal variable with mean of 95 and standard deviation of 6,
find the probability that x is between 90 and 100.
7. The five number summary for scores on a statistics exam is 11, 35, 61, 70,
79. In all, 380 students took the test. About how many had scores
between 35 and 61?
a) 26
b) 25
c) 76
d) 95
e) 190
8. What are the numbers used in making a box-and-whisker plot?
(a) Low value, Q1, mean, Q3, high value
(b) Low value, Q1, median, Q3, high value
(c) s, mean, s2, interquartile range
(d) Q1, Q2, Q3
(e) Low value, interquartile range, high value
9. Adult IQ scores have a bell-shaped distribution with a mean of 100 and a
standard deviation of 15. Use the Empirical Rule to find the percentage of
adults with scores between 70 and 130. (hint: sketch bell curve)
(a) 100%
(b) 95%
(c) 68%
(d) 99.7%
(e) 50%
10. If z is the standard normal variable (Z-score), find P(0 < z < 1.25).
For a distribution that is skewed to the left, usually
(a) the mean will be larger than the median
(b) the median will be larger than the mean
(c) the first quartile will be larger than the third quartile
(d) the standard deviation will be negative
(e) the minimum will be larger than the maximum
12. If event A is uncertain to occur, what is P(A)?
(a) 0.25
(b) 0.5
(c) 0.75
(d) 0
(e) 1
13. A normal distribution was transformed to a standard normal distribution.
The original  and  were 17 and 3.4, respectively. For z=2, what is the
corresponding x value?
(a) 11.9
(b) 7
(c) 37.4
(d) 23.8
(e) 18.7
14. The area under the standard normal curve corresponding to -0.3<Z<1.6 is
a) 0.3273
b) 0.4713
c) 0.5631
d) 0.9542
e) None of the above
15. The delivery time for a package sent within the United States is normally
distributed with mean of 4 days and standard deviation of approximately 1
day. If 300 packages are being sent, how many packages will arrive in less
than 3 days?
16. A community college student interviews everyone in a statistics class to
determine who owns a car. What sampling technique is used?
a) cluster
b) stratified
c) systematic
d) random
17. Make a stem-and-leaf diagram for the following data:
89, 98, 60, 76, 68, 86, 63, 66, 65, 94, 83, 85, 76, 62, 75