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Below are survival times (in days) of 13 guinea pigs that were injected with a bacterial infection in a medical study:
91 83 84 79 91 93 95 97 97 120 101 105 98


Are there any outliers in the data set above? Use the 1.5 IQR rule to check.


Q1 =


Q3 =


IQR =


IQR(1.5) =


Q3 + IQR(1.5) =
(Upper outlier)

Q1 - IQR(1.5) =
(Lower outlier)

Name any outliers in the set of data:

Sagot :

Outliers are data that are relatively far from other data elements.

The dataset has an outlier and the outlier is 120

The dataset is given as:

  • 91 83 84 79 91 93 95 97 97 120 101 105 98

Sort the dataset in ascending order

  • 79 83 84 91 91 93 95 97 97 98 101 105 120

The lower quartile (Q1)

The Q1 is then calculated as:

[tex]Q1 = \frac{N +1}{4}th[/tex]

So, we have:

[tex]Q1 = \frac{13 +1}{4}th[/tex]

[tex]Q1 = \frac{14}{4}th[/tex]

[tex]Q1 = 3.5th[/tex]

This is the average of the 3rd and the 4th element

[tex]Q1 = \frac{1}{2} \times (84 + 91)[/tex]

[tex]Q1 = 87.5[/tex]

The upper quartile (Q3)

The Q3 is then calculated as:

[tex]Q3 = 3 \times \frac{N +1}{4}th[/tex]

So, we have:

[tex]Q3 = 3 \times \frac{13 +1}{4}th[/tex]

[tex]Q3 = 3 \times 3.5th[/tex]

[tex]Q3 = 10.5th[/tex]

This is the average of the 10th and the 11th element.

[tex]Q_3 =\frac12 \times (98 + 101)[/tex]

[tex]Q_3 =99.5[/tex]

The interquartile range (IQR)

The IQR is then calculated as:

[tex]IQR = Q_3 -Q_1[/tex]

[tex]IQR = 99.5 - 87.5[/tex]

[tex]IQR = 12[/tex]

Also, we have:

[tex]IQR(1.5) = 12 \times 1.5[/tex]

[tex]IQR(1.5) = 18[/tex]

The outlier range

The lower and the upper outlier range are calculated as follows:

[tex]Lower = Q_1 - IQR(1.5)[/tex]

[tex]Lower = 87.5- 18[/tex]

[tex]Lower = 69.5[/tex]

[tex]Upper = Q_3 + IQR(1.5)[/tex]

[tex]Upper = 99.5 + 18[/tex]

[tex]Upper = 117.5[/tex]

120 is greater than 117.5.

Hence, the dataset has an outlier and the outlier is 120

Read more about outliers at:

https://brainly.com/question/9933184