Question

What does A with a line over it mean in statistics?

Answer 1

It might depend on the context, but the line over a variable usually means its the average of the variables values. I'll post an example in a second. It's common in statistics!

Answer 2

\(x_1 = 3\\x_2 = 5\\x_3=1\\x_4=3\)
Then...
\(\bar x=\dfrac{3+5+1+3}{4}=\dfrac{12}{4}=3\)

Answer 3

\(x\) might be things like the number of cookies eaten in one day, or something like that. Then all the subscripts, the \(_1\), \(_2\), \(_3\), and \(_4\), indicate the day number.

Answer 4

My professor put it on his practice quiz and didn't explain it.
It is not even in the book.

Answer 5

So, \(\sf P(\bar A\ and\ B)\)
Is this a logic class? Or math proofs? I think sometimes the line over might indicate "not", like, an element not include in set \(A\). So, what class is this? I might be able to help better if I know!

Answer 6

It is an intro stats class

Answer 7

Okay, then the line over A probably means the average of \(A\).
What is the whole question, so I can see if it makes sense!

Answer 8

He also put on the quiz the Union and Intersect symbols which are also NOT in the book. And he barely talked about the symbols. He assumed we knew.

Answer 9

And I don't like it when professors assign new things for homework, haha! It's like they're the teacher, but you'll have to go somewhere else to learn since it's out of school. Hopefully he doesn't mind if the answers aren't all good. :)

Answer 10

That is ridiculous. Again, then, he could be using it as the "not."

Answer 11

So, read it like "not A and B."

So, I guess you know some set stuff, if you were exposed to unions and intersections?

Answer 12

Right, he wrote on the board, P (A union B) and asked us what it meant. Noone said anything and he was surprised. I told him it wasn't in the book and he said you can't get everything from the textbook.
Then why the * are you asking us for it and why did you assign this book?

Answer 13

I guess \(A\) and \(B\) are sets. Then "\(A\) and \(B\)" means you want to talk about the elements that are in both \(A\) and \(B\), which is where the sets "intersect." That looks like \(A\cap B\) in one notation.

Sets are used in statistics, too. It's just like \(X\) is the set containing \(x_1\), \(x_2\) and so on. And there might be another set for how many cookies ANOTHER person eats each day, like \(Y\). After you put in all the numbers for the \(x_1\) stuff and \(y_1\) stuff, the intersection will be easier to see. If there is a number in both, then it is in the intersection \(X\cap Y\).

Answer 14

The problem is a table

Gender Bonds Stocks Balanced
male .18 .20 .25
female .12 .1 .15

There are two parts to the question
Find P(A with bar over it and B)
Find P(A with bar over and B with bar over it)
Sorry I don't know how to make that symbol.

Answer 15

Ah! \(P\) is probably the "power set." Does that sound familiar?

Answer 16

power set?

Answer 17

I guess not! It is often written as \(P(something)\). And I think P might be written fancily. Power set is a set of... sets...
Do you know what a subset is?

Answer 18

No I don't. It is a intro to Business stats class if that means anything.
It is a requirement.

Answer 19

I see. Well, it's important for all statistics, especially for working on probability.

A "proper subset" is a set that contains no more than some of the elements of another set. Take away the "proper" and it is just a subset, where all of its elements are within another set.
The symbol for subset is \(\subset\) or \(\supset\). For proper subsets, you will see \(\subseteq\) or \(\supseteq\). If \(A\) is a subset of \(B\), then you say \(A\subset B\). If \(A\) is a proper subset of \(B\), you say \(A\subseteq B\). That's what I learned, I think.

So, \(A=[1,\ 2, 3]\), we'll say. And so there are subsets of \(A\), like
\([1]\) \([2]\) \([3]\)
\([1,2]\) \([1,3]\) \([2,3]\)
and \([1,2,3]\).

The powerset is the set of \(A\) is all of those subsets!
\(P(A)=[\ [1]\) \([2]\) \([3]\) \([1,2]\) \([1,3]\) \([2,3]\) \([1,2,3]\) \(]\)

I have to go, take care!

Answer 20

"Welcome to OpenStudy. I can guide regarding this useful site; ask your doubts from me, for it you can message me. Please use the chat for off topic questions. And remember to give the helper a medal, by clicking on "Best Answer". We follow a code of conduct, ( http://openstudy.com/code-of-conduct ). Please take a moment to read it."

Answer 21

I guess I should have used commas:

\(P(A)=\large\left[\normalsize [1],\ [2],\ [3],\ [1,2],\ [1,3],\ [2,3],\ [1,2,3] \right]\)