Interquartile Range and Outliers

What does the interquartile range (IQR) measure in a data set?

• The total number of data points

• The spread of all values

• The middle 50% of data

• The difference between max and min

Which formula is used to calculate IQR?

• Q2 - Q1

• Q3 + Q1

• Q3 - Q1

• Q3 ÷ Q1

If Q1 = 30 and Q3 = 42, what is the IQR?

• 72

• 12

• 18

• 6

Outliers are values that fall...

• Within 1 standard deviation

• Outside the lower and upper boundaries

• Below Q1 only inside the minimum

• Above Q3 only inside the maximum

Why is IQR better than range in identifying spread?

• It's faster to calculate

• It uses only the smallest values

• It's not affected as much by outliers

• It shows the total variation

A data set has Q1 = 15 and Q3 = 35. What is the upper outlier boundary?

• 65

• 50

• 35

• 70

Which data point is an outlier in this set? {6, 8, 10, 12, 14, 16, 90}

• 6

• 90

• 8

• 14

In a box plot, how can you spot an outlier?

• It's in the center of the box

• It's the tallest value

• It's a dot beyond the whiskers

• It's always below Q1

Data set: {5, 7, 9, 10, 11, 13, 15}. What is the IQR?

• A. 6

• B. 4

• C. 10

• D. 8

A value is 5 units below the lower boundary. What does this mean?

• It's a lower outlier

• It's the median

• It's an upper outlier

• It's the minimum value