Question

A random walker is observed to take a total of N steps, n of which are to the right (and the rest n^' are to the left). Suppose that a curious observer finds that on ten successive nights the walker takes N = 20 steps and that the values of n are given successively by 14, 13, 11, 12, 11, 12, 16, 16, 14, 8.

(a) Calculate n, n^2, and σ_n. You can use this information to make two estimates of p, the probability of a step to the right.

Answer 1

p = 0.635

Explanation:

A step to the right is n and on ten different days, it was recorded to be

14, 13, 11, 12, 11, 12, 16, 16, 14, 8.

n = average of all the steps,

The average is the sum of variables divided by the number of variables

Average = (14+13+11+12+11+12+16+16+14+8)/10

Average = 12.7 steps.

σₙ² = variance of n

Variance is an average of the squared deviations from the mean.

[Σ(x - xbar)²/N]

Σ(x - xbar)² = (14-12.7)² + (13- 12.7² + (11-12.7)² + (12-12.7)² + (11-12.7)² + (12-12.7)² + (16-12.7)² + (16-12.7)² + (14-12.7)² + (8-12.7)² = 54.1

Variance = σₙ² = (54.1/10) = 5.41

standard deviation = σₙ = √(variance) = √5.41 = 2.326.

The proportion, p can be computed in two ways.

Mean = Np or standard deviation = √[Np(1-p)]

where N = total number of steps = 20

Mean = 12.7 = 20p

p = (12.7/20) = 0.635

Or

Standard deviation = 2.326 = √[20p(1-p)]

5.41 = 20p - 20p²

20p² - 20p + 5.41 = 0

Solving the quadratic equation,

p = 0.5 + 0.143i or p = 0.5 - 0.143i

not a unique or feasible solution, hence, the probability of a step to the right remains p = 0.635

Hope this Helps!!!