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:
I don't know but use this app on your phone called mw and it should help
Step-by-step explanation:
Answer choice B is correct
Answer:
Step-by-step explanation:
So, we have-
(6 x .1) + (3 x .01) + (2 x .001)
So, we will solve inside of the parenthesis first.
6 x .1 = <u>.6</u>
So, we got that settled next-
3 x .01 = <u>.03</u>
We got that settled last-
2 x .001 = <u>.002</u>
Lastly, we add them all.
.6 + .03 + .002 = .632
Now we compare.
.632 > .629
So, there is your answer!
Hope this helps!
