Answer:
Use the normal distribution if the population standard deviation is known.
Use the student's t distribution when the population standard deviation is unknown.
Explanation:
A mound-shaped distribution refers to the normal distribution.
A good sample size for testing against the normal distribution should be
n >= 30.
The condition for the sample size is satisfied.
However, we are not given the population standard deviation, therefore it is assumed to be unknown.
Therefore the student's t distribution should be used.
Answer: 13/12
Step-by-step explanation:
Common denominator:12
9/12 plus 4/12 equals 13/12 equals 1 1/12
Answer:
100,80
Step-by-step explanation:
The opposite angle theorem states that, : "When two lines cross four angles are created and the opposite angles are equal."
y°=80°
Now, check that , x° and y° are in one straight line. A straight line has angle of 180°. So x° and y° should sum up to 180°
x° + y° = 180°
x° + 80° = 180°
x° = 100°
Assuming a normal distribution we find the standardized z scores for a:-
z1 = (80 - 180) / 25 = = -100/25 = -4
z2 = (280-180) / 25 = 4
Required P( -4 < z < 4) from the tables is >99.9%
b
z1 = 130-180 / 25 = -2
z2 = 230-180 / 25 = 2
from tables probability is 2* 0.4773 = 95.46 %
