Question

The dataset below represents the population densities per square mile of land area in 15 states in the 2010 U.S. Census. What is the interquartile range?

Answer 1

The Interquartile range is 188

Explanation:

Missing Data:

1,19,35,43,49,55,63,94,105,110,175,231,239,351,738

Required

Determine the Interquartile range (IQR)

The given data is ordered already.

First, we need to determine the median

For odd number of data

Median = ½(n + 1)th

In this case, n = 15; so

Median = ½(15 + 1)th

Median = ½(16)th

Median = 8th

This implies that the median is at the 8th position.

So, we have:

1,19,35,43,49,55,63 ----> Lower

(94) ---- Median

105,110,175,231,239,351,738 ---- Upper

Next, we determine the median of the lower and upper sets.

These are called lower quartile (Q1) and upper quartile (Q3) respectively

Lower: 1,19,35,43,49,55,63

Number of data, n = 7

Q1 = ½(n + 1)th

Q1 = ½(7 + 1)th

Q1 = ½(8)th

Q1 = 4th position

From the list of data in the lower set,

Q1 = 43

Upper: 105,110,175,231,239,351,738

Number of data, n = 7

Q3 = ½(n + 1)th

Q3 = ½(7 + 1)th

Q3 = ½(8)th

Q3 = 4th position

From the list of data in the upper set,

Q3 = 231

IQR is then calculated as thus:

IQR = Q3 - Q1

IQR = 231 - 43

IQR = 188