math 10 4th quarter measures of position of groped data
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Measures of Position for Grouped Data
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Measures of Position for Grouped Data QUARTILES DECILES PERCENTILES
QUARTILES The steps in the computation of the median are also followed in the computation of Q 1 and Q 3 . To calculate the median, determine first the median class. In the same manner, the Q 1 class and the Q 3 class must be determined first before computing for Q 1 and Q 3 . The Q 1 class is the class interval where the th score is contained while the class interval that contains the th score is the Q 3 class. Q 1 and Q 3 (Grouped Data) N 4 3N 4
FORMULA Q 1 and Q 3 (Grouped Data) where X LB = lower boundary of Q 1 class N = total frequency cf b = cumulative frequency before Q 1 class fq 1 = frequency of the Q 1 class i = size of the class interval where X LB = lower boundary of Q 3 class N = total frequency cf b = cumulative frequency before Q 3 class fq 3 = frequency of the Q 3 class i = size of the class interval
EXAMPLE The following table shows the daily wages of 40 workers. Daily Wages ( ₱) Frequency 426 - 450 3 401 – 425 12 376 – 400 9 351 – 375 8 326 – 350 5 301 - 325 3 Find Q 1 and Q 3 N = 40
EXAMPLE Solution : compute for the value of Q 1 . Daily Wages ( ₱ ) Frequency < cf 426 - 450 3 401 – 425 12 376 – 400 9 351 – 375 8 326 – 350 5 301 - 325 3 N = 40 3 8 16 25 37 40 (1 st – 3 rd ) (4 th – 8 th ) (9 th – 16 th ) (17 th – 25 th ) (26 th – 37 th ) (38 th – 40 th ) Class Interval: 351 - 375 X LB = 350.5 cf b = 8 fq 1 = 8 = 25 Q 1 class: N 4 = 40 4 or 10 th
EXAMPLE Solution : compute for the value of Q 1 . Class Interval: 351 - 375 X LB = 350.5 cf b = 8 fq 1 = 8 = 25 Q 1 class: N 4 = 40 4 or 10 th There are 25% of the daily wages are below and 75% are above
EXAMPLE Q 3 class: 3N 4 = 3(40) 4 or 30 th Class Interval: 401 - 425 X LB = 400.5 cf b = 25 fq 3 = 12 = 25 There are 75% of the daily wages are below and 25% are above Solution : compute for the value of Q 3 .
The deciles are the score-points that divide a distribution into ten equal parts. The deciles are computed in the same way as the median, the quartile, and the percentiles were calculated. The Deciles (D 1 , D 2 , D 3 ,…, D 9 ) Grouped Data DECILES
FORMULA Deciles (Grouped Data)
EXAMPLE Use the frequency distribution to calculate a. D 2 b. D 5 c. D 8 Class Interval f < cf 134 - 139 10 50 128 – 133 9 40 122 – 127 8 31 116 – 121 1 23 110 – 115 5 22 104 – 109 2 17 98 – 103 9 15 92 – 97 5 6 86 - 91 1 1 N = 50 D 2 class: 2N 10 = 2(50) 10 or 10 th Class Interval: 98 - 103 X LB = 97.5 cf b = 6 fd 2 = 9 = 6 20% are below 100.17 and 80% are above 100.17
EXAMPLE Use the frequency distribution to calculate a. D 2 b. D 5 c. D 8 Class Interval f < cf 134 - 139 10 50 128 – 133 9 40 122 – 127 8 31 116 – 121 1 23 110 – 115 5 22 104 – 109 2 17 98 – 103 9 15 92 – 97 5 6 86 - 91 1 1 N = 50 D 5 class: 5N 10 = 5(50) 10 or 25 th Class Interval: 122 - 127 X LB = 121.5 cf b = 23 fd 5 = 8 = 6 50% are below and above 123
EXAMPLE Use the frequency distribution to calculate a. D 2 b. D 5 c. D 8 Class Interval f < cf 134 - 139 10 50 128 – 133 9 40 122 – 127 8 31 116 – 121 1 23 110 – 115 5 22 104 – 109 2 17 98 – 103 9 15 92 – 97 5 6 86 - 91 1 1 N = 50 D 8 class: 8N 10 = 8(50) 10 or 40 th Class Interval: 128 - 133 X LB = 127.5 cf b = 31 fd 8 = 9 = 6 80% are below 133.5 and 20% are above 133.5
PERCENTILES Finding P c for ungrouped data is seldom used because it involves a larger population. Hence, the formula for the computation of P c for grouped data is generally preferred. The steps in the computation of the median are also to be followed in the computation of the percentiles. P 1 , P 2 , P 3 , …, P 98 , P 99 (Grouped Data)
FORMULA Percentiles (Grouped Data) where X LB = lower boundary of P 5 class N = total frequency cf b = cumulative frequency before P 5 class fp 5 = frequency of the P 5 class i = size of the class interval where X LB = lower boundary of P 80 class N = total frequency cf b = cumulative frequency before P 80 class fp 80 = frequency of the P 80 class i = size of the class interval
EXAMPLE The table below shows the hourly wages of the 50 workers in the Paradise Farm. Calculate: a. P 10 b. P 30 c. P 75 Hourly Wages of 50 Workers in Paradise Farm Class Interval f < cf 134 - 139 10 128 – 133 9 122 – 127 8 116 – 121 1 110 – 115 5 104 – 109 2 98 – 103 9 92 – 97 5 86 - 91 1 N = 50 1 6 15 17 22 23 31 40 50
EXAMPLE The table below shows the hourly wages of the 50 workers in the Paradise Farm. Hourly Wages of 50 Workers in Paradise Farm Class Interval f < cf 134 - 139 10 128 – 133 9 122 – 127 8 116 – 121 1 110 – 115 5 104 – 109 2 98 – 103 9 92 – 97 5 86 - 91 1 N = 50 1 6 15 17 22 23 31 40 50 P 10 class: 10N 100 = 10(50) 100 or 5 th Class Interval: 92 - 97 X LB = 91.5 cf b = 1 fp 10 = 5 = 6 10% of the workers are below ₱ 96.3 and 90% are above ₱ 96.3.
EXAMPLE The table below shows the hourly wages of the 50 workers in the Paradise Farm. Hourly Wages of 50 Workers in Paradise Farm Class Interval f < cf 134 - 139 10 128 – 133 9 122 – 127 8 116 – 121 1 110 – 115 5 104 – 109 2 98 – 103 9 92 – 97 5 86 - 91 1 N = 50 1 6 15 17 22 23 31 40 50 P 30 class: 30N 100 = 30(50) 100 or 15 th Class Interval: 98 - 103 X LB = 97.5 cf b = 6 fp 30 = 9 = 6 30% of the workers are below ₱ 103.5 and 70% are above ₱ 103.5.
EXAMPLE The table below shows the hourly wages of the 50 workers in the Paradise Farm. Hourly Wages of 50 Workers in Paradise Farm Class Interval f < cf 134 - 139 10 128 – 133 9 122 – 127 8 116 – 121 1 110 – 115 5 104 – 109 2 98 – 103 9 92 – 97 5 86 - 91 1 N = 50 1 6 15 17 22 23 31 40 50 P 75 class: 75N 100 = 75(50) 100 or 37.5 Class Interval: 128 - 133 X LB = 127.5 cf b = 31 fp 75 = 9 = 6 75% of the workers are below ₱ 131.83 and 25% are above ₱ 131.83.
Percentiles are used when you need to know the relative standing of a score or value. For example, a grade 10 student who has a score of 38 from a 50-item test during online assessment, and he wants to know his relative standing in relation to the 250 grade-10 students handled by a particular teacher. If he is in the 125th position, what is his corresponding percentile? Ans. 50th percentile (P50). Solution: Solve for k using the locator L = 𝑘𝑛 100 where L = 125, and n = 250 125 = 𝑘 (250) 100 so k = 50. This means that there are 50% grade 10 students, or 125 students scored less than or equal to 38. Generalization: