WGU C955 Probability and Statistics Objective
Assessment Exam (2025 graded A+)
Simpson's Paradox - Answer- When split up, each data set can have a pattern which goes away
when all the data is combined.
Only way to prove causation - Answer- Experiments, because they account for lurking variables
Observational study - Answer- A type of study where we measure or survey members of a
sample without trying to affect them. Cannot prove causation.
quantitative data - Answer- Quantitative data consists of data values that are numbers,
representing quantities that can be counted or measured.
The Empirical Rule - Answer- According to The Empirical Rule, approximately 68% of the data
points in a dataset will be within 1 standard deviation of the mean. 95% of all values are within 2
standard deviations of the mean.
Normal distribution - Answer- In a normal distribution data is symmetrical, so the mean,
median, and mode are all equal.
measure of spread - Answer- Measures of spread describe how similar or varied the set of
observed values are for a particular variable (data item). Measures of spread include the range,
quartiles and the interquartile range, variance and standard deviation.
Standard Deviation Rule 2 and 3 deviations - Answer- According the the Standard Deviation
Rule, approximately 2.35 percent of all values will fall between 2 and 3 standard deviations
above the mean.
How are the mode and mean of a sample related if the distribution is positively skewed? -
Answer- The mode is less than the mean.
,Experimental study - Answer- A study where you split subjects up randomly and impose a
change on one group to study the effect; can prove causation
Prospective study - Answer- Is a study that's done over time to find results / A study watching
for outcomes during the study period
Retrospective study - Answer- A study that looks backwards to assess outcomes and possible
causes after the fact
Control group - Answer- randomly assign people or things to groups. One group receives a
treatment and the other group does not. This is the group that does not receive treatment
Placebo - Answer- A substance or procedure that has no effect used for comparison to the real
substance or procedure
Placebo effect - Answer- A beneficial effect produced by the belief of the patient/subject, not by
the intervention itself.
Experimenter effect - Answer- When the persons running an experiment affects its results by
influencing the subjects inadvertently
Open question - Answer- A question that gives the responder freedom to answer in many
different ways -- harder to analyze with statistics.
Closed question - Answer- A question with limited choices, e.g. multiple choice or yes/no.
Easier to analyze statistically.
Unbalanced response - Answer- Giving more options that are negative than positive options (or
vice versa) which biases the responses towards the more common option
, Matched pairs - Answer- Grouping two similar subjects and giving different
treatments/procedures to each in order to compare the differences. For example, having one twin
take a medication while the other twin does not.
Blind experimental study - Answer- When information of a study isn't revealed to the
participants
Double Blind Study - Answer- When information of study is hidden from the researcher and the
participant.
Population - Answer- The entire group you are trying to describe or understand.
A set of data is normally distributed with a mean of 85 and standard deviation 20. The data point
values that fall within one standard deviation range from ___________ to ___________? -
Answer- We know that the standard deviation is 20. To obtain the values that are one standard
deviation above and below the mean, we do the following: To obtain the first value, we will
subtract 20 from the mean: 85 −20 =65 To obtain the second value, we will add 20 to the mean:
85 +20 =105 Therefore, the data values that will fall within 1 standard deviation of the mean will
range from 65 to 105.
best used to display categorical data - Answer-
How are the mean, median, and mode of a sample related if the distribution is normally
distributed? - Answer- The values are all equal
IQR (interquartile range) - Answer- Q3-Q1
standard deviation - Answer- Using the Standard Deviation Rule, we know that when data is
normally distributed, 50% of the values fall above the mean, and 50% of the values fall below
the mean.
population sample from a box plot. - Answer- It is not possible to estimate the size of the
population sample from a box plot.
Assessment Exam (2025 graded A+)
Simpson's Paradox - Answer- When split up, each data set can have a pattern which goes away
when all the data is combined.
Only way to prove causation - Answer- Experiments, because they account for lurking variables
Observational study - Answer- A type of study where we measure or survey members of a
sample without trying to affect them. Cannot prove causation.
quantitative data - Answer- Quantitative data consists of data values that are numbers,
representing quantities that can be counted or measured.
The Empirical Rule - Answer- According to The Empirical Rule, approximately 68% of the data
points in a dataset will be within 1 standard deviation of the mean. 95% of all values are within 2
standard deviations of the mean.
Normal distribution - Answer- In a normal distribution data is symmetrical, so the mean,
median, and mode are all equal.
measure of spread - Answer- Measures of spread describe how similar or varied the set of
observed values are for a particular variable (data item). Measures of spread include the range,
quartiles and the interquartile range, variance and standard deviation.
Standard Deviation Rule 2 and 3 deviations - Answer- According the the Standard Deviation
Rule, approximately 2.35 percent of all values will fall between 2 and 3 standard deviations
above the mean.
How are the mode and mean of a sample related if the distribution is positively skewed? -
Answer- The mode is less than the mean.
,Experimental study - Answer- A study where you split subjects up randomly and impose a
change on one group to study the effect; can prove causation
Prospective study - Answer- Is a study that's done over time to find results / A study watching
for outcomes during the study period
Retrospective study - Answer- A study that looks backwards to assess outcomes and possible
causes after the fact
Control group - Answer- randomly assign people or things to groups. One group receives a
treatment and the other group does not. This is the group that does not receive treatment
Placebo - Answer- A substance or procedure that has no effect used for comparison to the real
substance or procedure
Placebo effect - Answer- A beneficial effect produced by the belief of the patient/subject, not by
the intervention itself.
Experimenter effect - Answer- When the persons running an experiment affects its results by
influencing the subjects inadvertently
Open question - Answer- A question that gives the responder freedom to answer in many
different ways -- harder to analyze with statistics.
Closed question - Answer- A question with limited choices, e.g. multiple choice or yes/no.
Easier to analyze statistically.
Unbalanced response - Answer- Giving more options that are negative than positive options (or
vice versa) which biases the responses towards the more common option
, Matched pairs - Answer- Grouping two similar subjects and giving different
treatments/procedures to each in order to compare the differences. For example, having one twin
take a medication while the other twin does not.
Blind experimental study - Answer- When information of a study isn't revealed to the
participants
Double Blind Study - Answer- When information of study is hidden from the researcher and the
participant.
Population - Answer- The entire group you are trying to describe or understand.
A set of data is normally distributed with a mean of 85 and standard deviation 20. The data point
values that fall within one standard deviation range from ___________ to ___________? -
Answer- We know that the standard deviation is 20. To obtain the values that are one standard
deviation above and below the mean, we do the following: To obtain the first value, we will
subtract 20 from the mean: 85 −20 =65 To obtain the second value, we will add 20 to the mean:
85 +20 =105 Therefore, the data values that will fall within 1 standard deviation of the mean will
range from 65 to 105.
best used to display categorical data - Answer-
How are the mean, median, and mode of a sample related if the distribution is normally
distributed? - Answer- The values are all equal
IQR (interquartile range) - Answer- Q3-Q1
standard deviation - Answer- Using the Standard Deviation Rule, we know that when data is
normally distributed, 50% of the values fall above the mean, and 50% of the values fall below
the mean.
population sample from a box plot. - Answer- It is not possible to estimate the size of the
population sample from a box plot.
