In West Texas, water is extremely important. The following data represent pH lev

Question

In West Texas, water is extremely important. The following data represent pH levels in ground water for a random sample of 102 West Texas wells. A pH less than 7 is acidic and a pH above 7 is alkaline. Scanning the data, you can see that water in this region tends to be hard (alkaline). Too high a pH means the water is unusable or needs expensive treatment to make it usable.† These data are also available for download at the Companion Sites for this text. For convenience, the data are presented in increasing order.

Look at an ogive of the data using five classes. What percent of the wells have a pH less than 8.15? (Round your answer to two decimal places.)
___%

Suppose a certain crop can tolerate irrigation water with a pH between 7.35 and 8.55. What percent of the wells could be used for such a crop? (Round your answer to two decimal places.)
___ %

x: pH of Ground Water in 102 West Texas Wells 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.1 7.1 7.1 7.1 7.1 7.1 7.1 7.1 7.1 7.1 7.2 7.2 7.2 7.2 7.2 7.2 7.2 7.2 7.2 7.2 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.4 7.4 7.4 7.4 7.4 7.4 7.4 7.4 7.4 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.6 7.6 7.6 7.6 7.6 7.6 7.6 7.6 7.6 7.7 7.7 7.7 7.7 7.7 7.7 7.8 7.8 7.8 7.8 7.8 7.9 7.9 7.9 7.9 7.9 8.0 8.1 8.1 8.1 8.1 8.1 8.1 8.1 8.2 8.2 8.2 8.2 8.2 8.2 8.2 8.4 8.5 8.6 8.7 8.8 8.8

Explanation / Answer

We have to give ogive of 5 classes

minimum value of ph = 7.0

maximum value of ph = 8.8

range = 8.8 - 7.0 = 1.8

so, class interval = 1.8/5 = 0.36

Percent of wells have pH less than 8.15 = (102-13)/ 102 = 0.8725 = 87.25%

Number of wells who has pH between 7.35 and 8.55 = Number of such wells/ Total number of wells =

59/102 = 0.5784 = 57.84%

Class interval (pH) Frequency CF 6.9 -7.2 28 28 7.3- 7.6 37 65 7.7- 8.0 17 82 8.1 - 8.4 15 97 8.5-8.8 5 102

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