Chapter 10 Statistical Measures and Displays
Lesson 10-3 Measures of Spread
Page 803
The table shows the number of golf courses in various states.
a. Determine the range of the data.
Subtract the least data value from the greatest data value.
1,465 – 437 = 1,028 golf courses
b. Determine the median and the first and third quartiles.
Order the numbers to find the median and the quartiles.
Q1
median = 923.5
Q3
437
456 513 650
893
954 1,018 1,038
1,117
1,465
The median is the average of 893 and 954.
893  954 1847

2
2
 923.5
The first quartile is the median of the data values less than 923.5.
Q1 = 513
The third quartile is the median of the data values greater than 923.5.
Q3 = 1,038
c. Determine the interquartile range.
Subtract the first quartile value from the third quartile value to find the
interquartile range.
1,038 − 513 = 525
Texas Math, Course 1
d. Determine any outliers in the data.
Multiply the interquartile range by 1.5.
525 × 1.5 = 787.5
Subtract 787.5 from the first quartile, 513, and add 787.5 to the third
quartile, 1,038, to find the limits for the outliers.
513 – 787.5 = –274.5
1,038 + 787.5 = 1,825.5
There are no data values less than –274.5 or greater than 1,825.5. So, there
are no outliers.
Determine the median, the first and third quartiles, and the interquartile
range of the daily attendance at the water park: 346, 250, 433, 369, 422,
298.
Order the numbers to find the median and the quartiles.
Q1 median = 357.5
Q3
250
298
346
369
422
433
The median is the average of 346 and 369.
346 + 369 715
=
2
2
= 357.5
The first quartile is the median of the data values less than 357.5.
Q1 = 298
The third quartile is the median of the data values greater than 357.5.
Q3 = 422
Subtract the first quartile value from the third quartile value to find the
interquartile range.
422 − 298 = 124
Texas Math, Course 1