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Example Questions
Example Question #1 : How To Find Outliers
Use the following five number summary to determine if there are any outliers in the data set:
Minimum:
Q1:
Median:
Q3:
Maximum:
There is at least one outlier on the high end of the distribution and no outliers on the low end of the distribution.
There are no outliers.
There is at least one outlier on the high end of the distribution and at least one outlier on the low end of the distribution.
It is not possible to determine if there are outliers based on the information given.
There is at least one outlier on the low end of the distribution and no outliers on the high end of the distribution.
There are no outliers.
An observation is an outlier if it falls more than above the upper quartile or more than
below the lower quartile.
. The minimum value is
so there are no outliers in the low end of the distribution.
. The maximum value is
so there are no outliers in the high end of the distribution.
Example Question #1 : How To Find Outliers
For a data set, the first quartile is , the third quartile is
and the median is
.
Based on this information, a new observation can be considered an outlier if it is greater than what?
Use the criteria:
This states that anything less than or greater than
will be an outlier.
Thus, we want to find
where
.
Therefore, any new observation greater than 115 can be considered an outlier.
Example Question #61 : Data
You are given the following information regarding a particular data set:
Q1:
Q3:
Assume that the numbers and
are in the data set. How many of these numbers are outliers?
One
Four
Three
None of the numbers are outliers
Two
Two
In order to find the outliers, we can use the and
formulas.
Only two numbers are outside of the calculated range and therefore are outliers: and
.
Example Question #1 : How To Find Outliers
Use the following five number summary to answer the question below:
Min:
Q1:
Med:
Q3:
Max:
Which of the following is true regarding outliers?
There are no outliers in the lower side of the data set, but there is at least one outlier on the upper side of the data set.
There is at least one outlier in the lower side of the data set and at least one outlier in the upper side of the data set.
There is only one outlier in this entire data set.
There are no outliers in the upper side of the data set, but there is at least one outlier on the lower side of the data set.
There are no outliers in this data set.
There is at least one outlier in the lower side of the data set and at least one outlier in the upper side of the data set.
Using the and
formulas, we can determine that both the minimum and maximum values of the data set are outliers.
This allows us to determine that there is at least one outlier in the upper side of the data set and at least one outlier in the lower side of the data set. Without any more information, we are not able to determine the exact number of outliers in the entire data set.
Example Question #1 : How To Find Outliers
Which values in the above data set are outliers?
no outliers
Step 1: Recall the definition of an outlier as any value in a data set that is greater than or less than
.
Step 2: Calculate the IQR, which is the third quartile minus the first quartile, or . To find
and
, first write the data in ascending order.
. Then, find the median, which is
. Next, Find the median of data below
, which is
. Do the same for the data above
to get
. By finding the medians of the lower and upper halves of the data, you are able to find the value,
that is greater than 25% of the data and
, the value greater than 75% of the data.
Step 3: . No values less than 64.
. In the data set, 105 > 104, so it is an outlier.
Example Question #11 : Bivariate Data
A certain distribution has a 1st quartile of 8 and a 3rd quartile of 16. Which of the following data points would be considered an outlier?
An outlier is any data point that falls above the 3rd quartile and below the first quartile. The inter-quartile range is
and
. The lower bound would be
and the upper bound would be
. The only possible answer outside of this range is
.
Example Question #1 : How To Create Residual Plots
On a residual plot, the -axis displays the __________ and the
-axis displays __________.
independent variable; the dependent variable
independent variable;
dependent variable; residuals
residuals; the
residuals
residuals; the independent variable
independent variable;
A residual plot shows the difference between the actual and expected value, or residual. This goes on the y-axis. The plot shows these residuals in relation to the independent variable.
Example Question #12 : Bivariate Data
Example Question #11 : Bivariate Data
What transformation should be done to the data set, with its residual shown below, to linearize the data?
Nothing, the data set is already linear
multiply the independent variable by
take the log of the dependent variable
Add to the y-value of each data point
multiply the dependent variable by a constant k.
take the log of the dependent variable
Taking the log of a data set whose residual is nonrandom is effective in increasing the correleation coefficient and results in a more linear relationship.
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