In a large human population, cranial length is approximately normally distributed with a mean of 185.6 mm and a standard deviation of 12.7 mm. What is the probability that a random sample of size 10 from this population will have a mean less than than 180? a. 0.0174 b. 0.1357 c. 0.0823 d. -1.39

Respuesta :

Answer:

The correct option is  c

Step-by-step explanation:

From the question we are told that

   The mean is  [tex]\mu = 185.6 \ mm[/tex]

   The standard deviation is  [tex]\sigma = 12.7 \ mm[/tex]

   The sample size is  n = 10  

    Generally the standard error of the mean is mathematically represented as

      [tex]\sigma_{x} = \frac{\sigma}{\sqrt{n} }[/tex]

=>    [tex]\sigma_{x} = \frac{ 12.7}{\sqrt{ 10 } }[/tex]

=>    [tex]\sigma_{x} = 4.016[/tex]

Generally the probability that a random sample of size 10 from this population will have a mean less than than 180 is mathematically represented as

     [tex]P(X < 180 ) = P(\frac{ X - \mu }{\sigma_{x} } < \frac{180 - 185.6}{4.016} )[/tex]

[tex]\frac{X -\mu}{\sigma }  =  Z (The  \ standardized \  value\  of  \ X )[/tex]

    [tex]P(X < 180 ) = P(Z < - 1.394 )[/tex]

From the z table  the area under the normal curve to the left corresponding to    -1.394  is  

          [tex]P(X < 180 ) = P(Z < - 1.394 ) = 0.081659[/tex]

=>      [tex]P(X < 180 ) = 0.0823[/tex]