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The interquartile range on a TI-84 calculator can be found by entering a list of data values into the calculator and then using the 1-Var Stats command to find the q1 (lower quartile) and q3 (upper quartile) values. The interquartile range is then the difference between the q3 and q1 values. This number can be used to measure the spread of the data set, as it shows the range of the middle 50% of the data set.
The interquartile range, often denoted IQR, is a way to measure the spread of the middle 50% of a dataset.
It is calculated as the difference between the first quartile (Q1) and the third quartile (Q3) of a dataset.
Note that quartiles are simply values that split up a dataset into four equal parts.
The IQR is often used to measure the spread of values in a dataset because it’s known to be resistant to outliers. Since it only tells us the spread of the middle 50% of the dataset, it isn’t affect by unusually small or unusually large values.
This makes it a preferable way to measure dispersion compared to a metric like the range, which simply tells us the difference between the largest and the smallest values in a dataset.
The following step-by-step example shows how to calculate the IQR for the following dataset on a TI-84 calculator:
Dataset: 4, 6, 6, 7, 8, 12, 15, 17, 20, 21, 21, 23, 24, 27, 28
Step 1: Enter the Data
First, we will enter the data values.
Press Stat, then press EDIT. Then enter the values of the dataset in column L1:
Step 2: Find the Interquartile Range
Next, press Stat and then scroll over to the right and press CALC.
Then press 1-Var Stats.
In the new screen that appears, press Enter.
From this screen we can observe the values for the first quartile (Q1) and the third quartile (Q3) of the dataset:
- First quartile (Q1): 7
- Third quartile (Q3): 23
The interquartile range is calculated as Q3 – Q1, which would be 23 – 7 = 16.
This tells us that the spread of the middle 50% of values in the dataset is 16.