Stat 121 Exam 1 Practice Missed Q's

Front 1

To standardize means to
A. subtract the mean from a value and then divide by the standard deviation.
B. calibrate the data until they have a normal shape.
C. smooth out irregularities and remove outliers from the data set.
D. center the data set about zero.

Back 1

A. subtract the mean from a value and then divide by the standard deviation.

Front 2

A professor wishes to graphically display the exam scores for 18 students in his class. The scores ranged from 45% to 100%. You should recommend that he use
A. a histogram
B. a stem and leaf plot
C. a bar graph
D. a pie chart.

Back 2

B. a stem and leaf plot

Front 3

Scores on a standard IQ test are approximately normally distributed with a mean μ = 100 and a standard deviation σ = 15. If Joe’s score is 133, what percentage of the IQ’s are more than 2.5 standard deviations above the mean?
A. 10% B. 5% C. 2.5% D. 0.6% E. Impossible to determine.

Back 3

D. 0.6%

Front 4

Which one of the following statements is an INCORRECT statement concerning z-scores? A. Z-scores are generally between -3 and +3. B. Z-scores have a mean of zero and a standard deviation of 1. C. Z-scores have the same unit of measure as the data.
D. Z-scores have the same shape as the distribution of the data from which those Z-scores were calculated.

Back 4

Which one of the following statements is an INCORRECT statement concerning z-scores? A. Z-scores are generally between -3 and +3. B. Z-scores have a mean of zero and a standard deviation of 1. C. Z-scores have the same unit of measure as the data.
D. Z-scores have the same shape as the distribution of the data from which those Z-scores were calculated.

Front 5

The time it takes college freshmen to complete the Mason Basic Reasoning Test is normally distributed with a mean of 24 minutes and a standard deviation of 5 minutes. What symbol should be used to represent the mean of 24 minutes?
A. μ
B. σ
C. x-bar
D. s

Back 5

A - u

Front 6

Which one of the following does NOT have the same units of measure as the data? A. mean B. median
C. standard deviation D. interquartile range E. z-score

Back 6

E. z-score

Front 7

Two variables are confounded when A. they interact in their effects on the response variable. B. the effect of one variable impacts the other variable. C. the effect of one variable on the response variable cannot be separated from effect of the
other variable on the response variable. D. both variables are classified as lurking variables.

Back 7

C. the effect of one variable on the response variable cannot be separated from effect of the
other variable on the response variable

Front 8

Blocking should be used whenever
A. you want to remove variation
B. Individuals may be biased
C. Individuals are similar within the blocks
D. All of the above

Back 8

D. All of the above

Front 9

Jane, a student at BYU, decides to study opinions of BYU students concerning grading in religion classes. She obtains a roll from every religion class and randomly selects five students on each roll. This sampling is
A. simple random sampling.
B. multistagesampling.
C. stratified sampling.
D. convenience sampling.

Back 9

C. Stratified Sampling

Front 10

Why do we compare different treatment groups in experiments? A. To eliminate bias.
B. To enhance the placebo effect. C. To neutralize the effects of lurking variables and measure treatment differences. D. To remove extraneous variation from the experiment error. E. To measure and reduce chance variation.

Back 10

C. To neutralize the effects of lurking variables and measure treatment differences.

Front 11

What is a distribution of a random variable?
A. The range of the values of a variable as centered around the mean.
B. The numerical values placed on a histogram at varying points about the mean.
C. A list of the possible values of a variable together with how often each value occurs.
D. The position of a variable within an observed data set.

Back 11

C. A list of the possible values of a variable together with how often each value occurs.

Front 12

Lurking variables can be managed by each of the following except one. Which one is NOT a method for managing lurking variables? A. Using a control group with a placebo as a comparison for the treatment group. B. Randomly allocating experimental units to the treatments.
C. Designing the study so that the lurking variable is confounded with the explanatory variable. D. Bringing lurking variables into the experiment to form blocks.

Back 12

C. Designing the study so that the lurking variable is confounded with the explanatory variable.

Front 13

The standard deviation of a set of data is computed to be 8.2. If 10 is added to each data value, what can we say about the standard deviation of the new data set?
A. The standard deviation decreases.
B. The standard deviation increases.
C. The standard deviation stays the same.
D. Without recomputing the standard deviation it is impossible to say.

Back 13

C. St Dev stays the same.

Front 14

68. Interquartile range is all of the values between Q1 and Q3. T/F

Back 14

False

Front 15

69. Observational studies cannot have control groups.

Back 15

False

Front 16

70. All voluntary response samples are samples of convenience.

Back 16

True