The average score of 100 students taking a statistics final was 70 with a standard deviation of 7. Assuming a normal distribution, what test score separates the top 5% of the students from the lower 95% of students?

Respuesta :

Answer:

Hence, the answer is [tex]x>71.1515[/tex]

Step-by-step explanation:

We have,

[tex]n=100,\mu=70,\sigma=7[/tex]

The top percentage of the students is [tex]5\%[/tex]

The  lower percentage of the students is [tex]95\%[/tex]

The lowest [tex]95\%[/tex] is the left area from the normal distribution table, the area [tex]0.95[/tex] lies in the z-table

[tex]z=1.645[/tex]       from the z- table

[tex]P(z<1.645)=0.95\\P(z>1.645)=0.05\\z>1.645[/tex]

[tex]\frac{x-\mu}{\frac{\sigma}{\sqrt{\mu}} } >1.645\\x>1.645\times \frac{\sigma}{\sqrt{n}} +\mu[/tex]

   [tex]>1.645\times \frac{7}{\sqrt{100}} +70[/tex]

   [tex]\Rightarrow x>71.1515[/tex]