Let X be the national sat score. X follows normal distribution with mean μ =1028, standard deviation σ = 92
The 90th percentile score is nothing but the x value for which area below x is 90%.
To find 90th percentile we will find find z score such that probability below z is 0.9
P(Z <z) = 0.9
Using excel function to find z score corresponding to probability 0.9 is
z = NORM.S.INV(0.9) = 1.28
z =1.28
Now convert z score into x value using the formula
x = z *σ + μ
x = 1.28 * 92 + 1028
x = 1145.76
The 90th percentile score value is 1145.76
The probability that randomly selected score exceeds 1200 is
P(X > 1200)
Z score corresponding to x=1200 is
z = 
z = 
z = 1.8695 ~ 1.87
P(Z > 1.87 ) = 1 - P(Z < 1.87)
Using z-score table to find probability z < 1.87
P(Z < 1.87) = 0.9693
P(Z > 1.87) = 1 - 0.9693
P(Z > 1.87) = 0.0307
The probability that a randomly selected score exceeds 1200 is 0.0307
Answer:
25%
Step-by-step explanation:
difference between 8 and 10 is 2, so 8 would need to increase by 2 to get to 10.
2 is 1/4 of 8, and 1/4 is 25%
answer is 25%
Answers:
- a) Mean = 20.4
- b) New mean = 20
==================================================
Explanation:
To get the mean, we add up the scores and divide by 10 (because there are 10 scores at first)
28+13+4+12+32+22+13+22+26+32 = 204
204/10 = 20.4
The mean is 20.4
------------
For part b), we redo those steps shown above, but tack 16 onto the list. So we'll add up all the values (including that 16 at the end) and divide by 11 this time.
28+13+4+12+32+22+13+22+26+32+16 = 220
220/11 = 20
The new mean is 20.
The new mean is slightly smaller than the old mean. Notice how 16 is smaller than 20.4, so this new score pulls down the mean just a little bit.
Add the two angles and set them equal to 180, them solve for x
If there are 12 coins under the couch and every coin is either a nickel or a penny and together they are forming 32 cents then the equations which represent the problem will be x+y=12, 0.01x+0.05y=0.32. The correct option is B which is x+y=12, 0.01x+0.05y=0.32.
Given There are 12 coins and total money is 32 cents.
Let the number of pennies be x and the number of nickels be y.
According to question there are 12 coins so the first equation becomes:
x+y=12.
Then we have been told that together they amount to 32 cents.
We know that 1 penny is 1 cent coin and 1 nickel is 5 cent coin so the equation becomes :
1*x+5*x=32
x+5y=32
converting into dollar
0.01x+0.05y=0.32.
Hence the right equations showing the problem of nickel and pennies are x+y=12, 0.01x+0.05y=0.32.
Learn more about equations here brainly.com/question/2972832
#SPJ10
