Abby scored 87, 86, 93, and 89 on her first four history quizzes. What score does Abby need to get on her fifth quiz to have an
1 answer:
Answer:
(C) 100
Step-by-step explanation:
The average of a data set is just all the numbers added up divided by the amount of numbers.
If we already have 4 pieces of data and we're looking for one more, we have 5 data pieces.
This means that the sum of all of the numbers in the data set will be if the mean is 91.
We can find the missing value by adding up what we know and subtracting from 455.
So Abby needs a 100% on her fifth history quiz to have an average of 91 on all her quizzes.
Hope this helped!
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Answer:
<em>The 9th percentile of X is 44.96</em>
Step-by-step explanation:
<u>Percentiles for a Normal Distribution</u>
The standard normal distribution can be used for computing percentiles. For example, the median is the 50th percentile being the center value, the first quartile is the 25th percentile, and so on.
To compute percentiles of a normal distribution we can use the formula
Where is the mean,
is the standard deviation of the variable X, and z is the z-score value from the standard tables
The value of X can also be directly obtained from digital tables included in math packages and tools like Excel.
The Excel NORM.INV Function calculates the inverse of the cumulative Normal Distribution Function for a given value of p, and
.
We'll use the values
NORM.INV(0.09,53,6) results in 44.96 which means the 9th percentile of X is 44.96
We could have used the standard normal distribution, which only needs the value of p
That is the value of z, we now apply the formula
We get the very same result as before