High School

A population of values has a normal distribution with [tex]\mu = 35.9[/tex] and [tex]\sigma = 65.4[/tex]. You intend to draw a random sample of size [tex]n = 202[/tex].

Please show your answers as numbers accurate to 4 decimal places.

1. Find the probability that a single randomly selected value is between 35.4 and 42.8.
2. Find the probability that a sample of size [tex]n = 202[/tex] is randomly selected with a mean between 35.4 and 42.8.

Answer :

Therefore, the probability that a sample of size `n = 202` is randomly selected with a mean between `35.4` and `42.8` is `0.0919`.

The mean is `μ = 35.9` and standard deviation is `σ = 65.4`.To find the probability that a single randomly selected value is between 35.4 and 42.8, the standardized value (z-score) for 35.4 and 42.8 is calculated as follows:

z1 = (35.4 - μ) / σ

= (35.4 - 35.9) / 65.4

= -0.0076z2 = (42.8 - μ) / σ

= (42.8 - 35.9) / 65.4

= 0.1058

Now, probability `P` (35.4 < x < 42.8) is given by:

P = P(z1 < z < z2)

Here, z-table for calculating `P(z1 < z < z2)`.

`P(z1 < z < z2) = 0.1299`.

Therefore, the probability that a single randomly selected value is between 35.4 and 42.8 is `0.1299`.

To find the probability that a sample of size `n = 202` is randomly selected with a mean between `35.4` and `42.8`. the mean of a sample follows a normal distribution with mean

Now, z-score for `x = 35.4` and `x = 42.8` are calculated as follows:

z1 = (35.4 - μ) / (σ / [tex]\sqrt{(n)}[/tex])

[tex]= (35.4 - 35.9) / (65.4 / \sqrt{(202)})[/tex]

= -1.3705z2

= (42.8 - μ) / (σ / [tex]\sqrt{(n)}[/tex])

[tex]= (42.8 - 35.9) / (65.4 / \sqrt{(202)})[/tex]

= 1.6584

Now, the probability `P` that the sample mean is between `35.4` and `42.8` is:

P = P(z1 < z < z2)

Here, use z-table for calculating `P(z1 < z < z2)`.

We get `P(z1 < z < z2) = 0.0919`.

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