Answer to Question #331492 in General Chemistry for heshee

Question

The following pH data were collected in the analysis of water from an upstate New York lake as part of an acid rain study: 4.17, 4.20, 4.19, 4.23, 4.22, 4.14, 4.20, and 4.15. Calculate the following.

(a) mean

(b) median

(c) percent average deviation

(d) percent standard deviation

Answer 1

(a) Mean value = (4.17 + 4.20 + 4.19 + 4.23 + 4.22 + 4.14 + 4.20 + 4.15) / 8 = 4.1875

(b) Median value = (4.23 + 4.22) / 2 = 4.225 (even number of data)

(c) Percent average deviation = (|4.17 - 4.1875| + |4.20 - 4.1875| + |4.19 - 4.1875| + |4.23 - 4.1875| + |4.22 - 4.1875| + |4.14 - 4.1875| + |4.20 - 4.1875| + |4.15 - 4.1875|) / 8 × 100% = 0.205 / 8 × 100% = 2.56%

(d) Percent standard deviation = √{(4.17 - 4.1875)² + (4.20 - 4.1875)² + (4.19 - 4.1875)² + (4.23 - 4.1875)² + (4.22 - 4.1875)² + (4.14 - 4.1875)² + (4.20 - 4.1875)² + (4.15 - 4.1875)²} / 8 = 0.030 or 3.0%