Answer:
b. Because the probability of being 15 or more correct is 0.0207, it is likely that she is just guessing at the questions.
Step-by-step explanation:
-This is a binomial probability distribution with p=0.5, n=20 and x=15.
The function is expressed as:

We calculate the probability of guessing 15 or more correctly:

The probability of passing, guessing 15+ correctly, is 0.0207. This probability is very low and it is it is likely that she is just guessing at the questions
Answer:
52
Step-by-step explanation:
Given that :
Mean (m) = 78
Standard deviation (s) = 13
Score that is 2 standard deviations below the mean
Using the relation :
Zscore = (x - m) / s
2 standard deviations below the mean means a Zscore of - 2
Hence,
-2 = (x - 78) / 13
Cross multiply
-2 * 13 = x - 78
-26 = x - 78
x = - 26 + 78
x = 52
Score which is 2 standard deviations below the mean is 52
Can you Elaborate your question?
5m-n
Just replace m with 4 and n with 9
5(4)-9=20-9=11
Answer:
There are 120 1st graders at Sierra Elementary School this year
Step-by-step explanation:
Let n represent the total number of 1st graders at Sierra Elementary School
Since 45% of all 1st graders at Sierra Elementary School are female students and this year there are 54 female 1st graders, 45% of n is equal to 54
→ n(
) = 54
→ 45n = 5400
→ n = 120