A Statistics class is estimating the mean height of all female students at their college. They collect a random sample of 36 fem
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We want to find the mean of two elements in a set, given that we know the other elements of the set and the mean of the whole set.
The answer is: -490
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For a set with N elements {x₁, x₂, ..., xₙ} the mean is given by:
Here we know that:
- The mean of the set is 0.
- The set has 1000 elements.
- 998 of these elements are ones, the other two are A and B.
We want to find the mean of the values of A and B.
First, we can start by writing the equation for the mean:
We can rewrite this as:
And we have 998 ones, then:
Now we have B isolated.
With this, the mean of A and B can be written as:
So we can conclude that the mean of the other two numbers is -490.
If you want to learn more, you can read:
Answer:
Ann would need 3 h to complete the remainder of the Job.
Step-by-step explanation:
Step 1.
The "speed" that each girl has to do the work is determined as:
- Tina:
, it means that Tina complete one twelveth of the job each hour.
- Ann:
, it means the Ann completes one eighth of the job each hour.
Step 2.
The amount of work done by Tina in 9 hours, is obtain multiplying by the "speed" calculated in step 1:
Amount of work done= . It means that <em>Tina completes two thirds of the work in 9 h.</em>
Step 3.
The remaining job is calculated as . It means that <em>still remains is one third of the job to be completed</em>.
Step 4.
The time required for Ann to complete the job is calculated dividing the remaining of the job by the "speed" of Ann to do the job.
. It means that <em>Ann would complete the job in another 3 hours</em>.