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
14.
1. 7 × 7 = 49
2. 7 × 3 × 3 = 63
3. 7 × 3 × 4 = 84
4. 7 + 3 + 4 = 14
Hope that helps! Feel free to ask for a more explanation, if needed.
Basically you multiply the original length by the scale factor. So let's say there's a side length of 10 and the scale factor is .5, then you multiply 10 by .5 and get 5, that's all scale factor is . It can get larger/smaller, just depends on the number.
80% like crisps
75% of the 80% like chocolate.
What percent of the total are the children who like chocolate and crisps?
75% of 80% = 60%
This 60% of children like chocolate and crisps
