Question

X has a normal distribution with the given mean and standard deviation. Find the indicated probability. (Round your answer to four decimal places.) μ = 51, σ = 10, find P(36 ≤ X ≤ 56)

Answer 1

Answer:

0.6247

Step-by-step explanation:

The formula for calculating a Z-score is Z = (X - μ)/σ,

where x is the raw score

μ is the population mean

σ is the population standard deviation.

From the question,

μ = 51, σ = 10. We are to find P(36 ≤ X ≤ 56)

Step 1

Find the Probability of X ≤ 36

μ = 51, σ = 10

Z = (X - μ)/σ

Z = 36 - 51/ 10

Z = -15/10

Z = -1.5

We find the Probability of Z = -1.5 from Z-Table

P(X <36) = P(X = 36) = P(Z = -1.5)

= 0.066807

Step 2

Find the Probability of X ≤ 56

μ = 51, σ = 10

Z = (X - μ)/σ

Z = 56 - 51/ 10

Z = 5/10

Z = 0.5

We find the Probability of Z = 0.5 from Z-Table:

P(X < 56) = P(X = 56) = P(Z = 0.5)= 0.69146

Step 3

Find P(36 ≤ X ≤ 56)

P(36 ≤ X ≤ 56) = P(X ≤ 56) - P(X ≤ 36)

= P( Z = 0.5) - P(Z = -1.5)

= 0.69146 - 0.066807

= 0.624653

Approximately to 4 decimal places , P(36 ≤ X ≤ 56) = 0.6247