Answer:
Mean = 78.2
Standard deviation = 5.8
Step-by-step explanation:
Mathematically z-score;
= (x-mean)/SD
From the question;
12% of test scores were above 85
Thus;
P( x > 85) = 12%
P(x > 85) = 0.12
Now let’s get the z-score that has a probability of 0.12
This can be obtained from the standard normal distribution table and it is = 1.175
Thus;
1.175 = (85 - mean)/SD
let’s call the mean a and the SD b
1.175 = (85-a)/b
1.175b = 85 - a
a = 85 - 1.175b ••••••••(i)
Secondly 8% of scores were below 70
Let’s find the z-score corresponding to this proportion;
We use the standard normal distribution table as usual;
P( x < 70) = 0.08
z-score = -1.405
Thus;
-1.405 =( 70-a)/b
-1.405b = 70-a
a = 70 + 1.405b ••••••(ii)
Equate the two a
70 + 1.405b = 85 - 1.175b
85 -70 = 1.405b + 1.175b
15 = 2.58b
b = 15/2.58
b = 5.81
a = 70 + 1.405b
a = 70 + 1.405(5.81)
a = 78.16
So mean = 78.2 and Standard deviation is 5.8
Answer:
2.3%
Step-by-step explanation:
The formula to convert x into z distribution is
Where z is the test statistic
x is what we are looking for (in this case 37)
is the mean (in this case, it is 25)
is the standard deviation (we have 6)
<em>Plugging these into the formula, we get:</em>
Thus we can say we want 
<u>Note: </u> 
The table given is for any z where 
Thus, now we have:
0.0228 into percentage is 0.0228 * 100 = 2.28%
Rounded, we get 2.3%
Third answer choice is right.
Answer:it’s b
Step-by-step explanation:
On edn
I’ve never see the truth about coks so it’s 27 inches for sure if it was all the same as2,2 743+77482=747474
<span>1.Multiply the bottom number of the fraction by the whole number.
<span>2.Simplify the fraction (if needed)</span></span>
