Question

(1 pt) A data set consists of the 11 data points shown below, plus one additional data point. When the additional point is included in the data set, the sample standard deviation of the 12 points is computed to be 12.091. If it is known that the additional data point is 25 or less, find the value of the twelfth data point. 25, 41, 49, 25, 30, 13, 31, 34, 27, 54, 38 Value of the additional data point

Answer 1

Answer:

12.83

Step-by-step explanation:

S = 12.091

N = 12

We must find the 12th point, X

The formula of S² (variance) as a function of µ (media) is as follows:

S² = (1/N Ʃ Xi²) - µ²

S² = 146.2

Multiplying both members by N,  

N S² = Ʃ Xi² – N µ²

On the other hand,

µ = (25 + 41 + 49 + 25 + 30 + 13 + 31 + 34 + 27 + 54 + 38 + X) / 12

µ = (367 + X) / 12

Replacing,

12 x 146.2 = 13607 + X² – 12 (367 + X)² / 144

1754.4 = 13607 + X² – 0.0833 (134689 + 734 X + X²)

1754.4 = 13607 + X² – 11219.5 – 61.14 X – 0.0833 X²

0.92 X² – 61.14 X + 633.1 = 0

This is solved by finding the two values of X that satisfy the equation.

The solution requires solving the quadratic formula,

X12 = (-b ± √(b² - 4ac)) / 2a

The values are:

X1 = 12.83

X2 = 53.62

Since we know that the value is 25 or less, the answer is 12.83