Question

A normal distribution has a mean of μ=54 and a standard deviation of σ=6. What is the probability of randomly selecting a score less than X=51? What is the probability of selecting a Random sample of n=4scores with a mean less than m=51? What is the probability of selecting a sample of n=36scores with a mean less than m=51?

Answer 1

A)The probability of randomly selecting a score less than X=51 is 0.3085

B)The probability of selecting a Random sample of n=4scores with a mean less than m=51 is 0.1587

C)The probability of selecting a sample of n=36scores with a mean less than m=51 is 0.0013

Explanation:

Mean =
`\mu = 54`

Standard deviation =
`\sigma = 6`

A)What is the probability of randomly selecting a score less than X=51 i.e. P(x<51)?

Formula :
`Z =(x-\mu)/(\sigma)`

`Z=(51-54)/(6)`

Z=-0.5

Refer the Z table for p value

So, P(x<51)=0.3085

So,the probability of randomly selecting a score less than X=51 is 0.3085

B)What is the probability of selecting a Random sample of n=4scores with a mean less than m=51?

Formula :
`Z =(x-\mu)/((\sigma)/(√(n)))`

`Z=(51-54)/((6)/(√(4)))`

Z=-1

Refer the Z table for p value

So, P(x<51)=0.1587

So, the probability of selecting a Random sample of n=4scores with a mean less than m=51 is 0.1587

C) What is the probability of selecting a sample of n=36scores with a mean less than m=51?

Formula :
`Z =(x-\mu)/((\sigma)/(√(n)))`

`Z=(51-54)/((6)/(√(36)))`

Z=-3

Refer the Z table for p value

So, P(x<51)=0.0013

So,the probability of selecting a sample of n=36scores with a mean less than m=51 is 0.0013