The average weight of a professional football player in 2009 was pounds. Assume the population standard deviation is pounds. A random sample of professional football players was selected. Required:
a. Calculate the standard error of the mean.
b. What is the probability that the sample mean will be less than 230 pounds?
c. What is the probability that the sample mean will be more than 231 pounds?
d. What is the probability that the sample mean will be between 248 pounds and 255 pounds?

6.286;

0.0165

0.976

0.1995

Step-by-step explanation:

Given that :

Mean, μ = 243. 4

Standard deviation, σ = 35

Sample size, n = 31

1.)

Standard Error

S. E = σ / √n = 35/√31 = 6.286

2.)

P(x < 230) ;

Z = (x - μ) / S.E

P(Z < (230 - 243.4) / 6.286))

P(Z < - 2.132) = 0.0165

3.)

P(x > 231)

P(Z > (231 - 243.4) / 6.286))

P(Z > - 1.973) = 0.976 (area to the right)

4)

P(x < 248)

P(Z < (248 - 243.4) / 6.286))

P(Z < 0.732) = 0.7679

P(x < 255)

P(Z < (255 - 243.4) / 6.286))

P(Z < 1.845) = 0.9674

0.9674 - 0.7679 = 0.1995

let's cover over the formula of the vertex:

y = a(x – h)^2 + k

in this formula, (h,k) are the vertex, always remember that the positive or negative value of the vertex is based on the sign it has.

for example, if the vertex is -3,-6 then both the x and y value would have the positive sign attached to it and if it were a positive x and y value, then a negative sign would be attached to it.

with that being said, for our problem the x value is a positive one so we are looking for a number with a negative sign next to it, in this case the first and second choice.

however, for the first answer choice it isn't quite part of the formula so we know that the answer choice correctly displays the x value.

to confirm, we can see if the -1 fits correctly with the second answer choice, and as mentioned above a negative number will have a positive sign attached to it. so, for our problem we can see that -1 has been changed to +1, so we can confirm that the second answer choice is correct.

hence, our final answer is y=(x - 1)^2 + 1