The probability is 0.6962 for the given standard deviation.
What is standard deviation?
Standard Deviation is a measure that shows what quantity variation (such as unfold, dispersion, spread,) from the mean exists. the quality deviation indicates a “typical” deviation from the mean. it's a well-liked live of variability as a result of it returns to the first units of live of the info set.
Main body:
X - Binomial(n = 130, p = 0.5)
Binomial can be approximated to normal with: μ = np = 130*0.5 = 65
σ = √np(1 − p) - = √130* (0.5)(1 − 0.5)
σ = 5.7
P(55 ≤ X ≤ 69 )
Since we are approximating a discrete binomial distribution by continuous normal distribution, values between 54.5 and 68.5 both approximate to 55. Thus, "between 55 and 69" corresponds to continuous normal distribution with P(54.5 < X 68.5) after continuity correction.
Normal Distribution, x₁ = 54.5, x2 = 68.5, µ = 65, σ = 5.7
We convert this to standard normal using z =
z₁ = 54.5-65/ 5.7 ≈ - 1.84
z₂ = 68.5-65/ 5.7 ≈ 0.614
P(54.5 < X < 68.5) = P(- 1.84 < Z < 0.614)
= P(Z < 0.614) − P(Z <- 1.84)
= 0.7291 - 0.0329 (from z-table)
= 0.6962
Hence the probability is 0.6962
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