Algebra 1 Common Core Student Edition, Grade 8-9

Go t I t? 3. What do the medians tell you about the average monthly rainfalls for Miami

and New Orleans?

Per cen t i l es separate data sets into 100 equal parts. The percentile rank of a data value

is the percentage of data values that are less than or equal to that value.

Fi n d i n g a Pe r ce n t i l e R a n k

Multiple Choice Of 25 test scores, eight are less than or equal to 75. What

is the percentile rank of a test score of 75?

<3D8 CD 17 CO 32 CO 75

_ 8 _ W r i t e t h e r a t i o o f t h e n u m b e r o f t e s t s c o r e s l e s s t h a n o r

How else could you 25 equal t o 75 compar ed t o t he t ot al number of t est scor es,

find the percentile 8

rank? 25 = 0-32 ^ewr'te the fraction as a percent.

Yo u c o u l d so l v e t h e = 32 %

proport ion ^ ^

for p. The percentile rank of 75 is 32. The correct answer is C.

• 
  
  
  
  • G o t It? 4. a. Of the 25 scores in Problem 4, there are 15 scores less than or equal to 85.
    What is the percentile rank of 85?
    b. Reasoning Is it possible to have a percentile rank of 0? Explain.
  
  
  
  

^ Lesson Check

Do yo u k n o w H OW?

Identify the minimum, first quartile, median, third

quartile, and maximum of each data set. Then make a

box-and-whisker plot of each data set.

1. file sizes (megabytes): 54 100 84 124 188 48 256


2. daily atten d an ce:^2<?8x32 ?0 312fe 33


3. In the box-and-whisker plots below, which class has
   the greater interquartile range of arm spans?

Arm Spans (in.)

« l I I I l l l l l l l l l l l >

58 60 62 64 66 68 70 72

Class A • -

— , ____________________________ MATHEMATICAL

Do y o u UN DERSTAND? PRA CTI CES

4. Vocabulary Which portion of a box-and-whisker plot
   represents the interquartile range?


5. Students taking a make-up test receive the following
   grades: 77, 89, 88, 67, 91, 95, 83, 79, 81, and 65. Which
   grade has a percentile rank of 70?


6. Reaso n i n g About what percent of the data in a data
   set falls between the minimum value and the third
   quartile? Explain.


7. Erro r Analysis A test is graded on a scale from
   0 to 100. Your friend says that if you score a 78,
   your percentile rank must be 78. Is your friend
   correct? Explain.

Class B

c

Po w erAlg eb ra.com | Lesso n 12- 4 Box-and -W hisker Plot s^749