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MTH 220 May 25 Open Questions
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AvatarGreg Miller
8:27
There are LOTS of calculations in correlation/regression so that's why I wanted you guys/gals on this practice case tonight.
8:26
Yeah.. do that.. and if you don't get my numbers you can send it to me and we can fix it in Zoom..
Kasey
8:26
ok I'll rework and double check now
AvatarGreg Miller
8:26
You might have a little round off error like we talked about.. but the FINAL answer should be VERY close to -.933
8:25
and then overall, r = (-857.1428571)/(918.6696238) = -.933
Kasey
8:25
ok cool! Btw I'm excited about not having so much eraser mess when this class is over.  constantly dusting off my desk!
AvatarGreg Miller
8:24
the denominator should be square root of (1632.857143 * 516.8571429)...
8:23
it's ok.. I'm going to leave you the rest of the numbers in here so  you can come back and check...
Kasey
8:23
So sorry I know that's elementary but it's been forever
AvatarGreg Miller
8:23
Once you plug in the numbers from the five column chart.. the numerator of the r formula should give -857.1428571
8:22
Yes, I think you should do that.
Kasey
8:22
so do you recommend I always put my negative number in parenthesis. I thought I did that but I might have failed to with that one
AvatarGreg Miller
8:22
right.. squaring.. so all those should be positive.. but, I don't thing that's the only issue..
Kasey
8:22
oh no! -10 is not -100
AvatarGreg Miller
8:20
Ok.. all of them are right except the x squared column.. not 2978, but 3178... see its' that same (-10) squared = 100, thing again.
Kasey
x bar is 14.8571 and y bar is 16.8571
8:19
ok sum of x= 105 y=118 xsquared=2978 ysquared=2506 and xy= 896
AvatarGreg Miller
8:18
Let's start with the five column chart.. tell me your five totals
I mean.. the points are VERY close to a line.. the guess should be close to -1
8:17
No.. let's go over that.
Kasey
8:17
I got r=-.0012
8:16
Well now I'm wondering if I got the right answer because my r is lowed Thant the -.30
8:15
oh I see!
AvatarGreg Miller
8:13
I wanted you to make the scatterplot.. then compare it to the handout and make a guess for the actual number for r before calculating it... by comparing what you saw for our data to the handout pictures.
Kasey
look I'm cracking stats jokes!
8:13
I know it was between -1 and 1! lol jk
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AvatarGreg Miller
8:12
Oh ok.. what I meant was:
Kasey
8:12
Oh no but I solved for r.  I'm not sure what you mean.
AvatarGreg Miller
8:11
Yes, but did you actually guess a number for r?
Kasey
8:11
I guessed that we had a negative linear trend because as the x increases the y decreases.
AvatarGreg Miller
what'd you guess?
Don't try to do that.. I was talking purely the scatterplot for a "visual" guess
8:10
No.. you can't make a guess from the chart...
Kasey
8:09
Ok yes because I was unsure how to make a conclusion just by looking at the 5 column chart.  I can make some guess regarding the plot but wasn't sure about trends in the chart.
AvatarGreg Miller
8:09
It's hard with small dataset like that to make a guess (n=7)..it's easier when there are more points on the scatterplot
Kasey
8:07
I think it's the length.  They are usually longer or on legal paper and maybe they are yellow so you can look quickly and tell it's a legal pad and is therefore longer... that's my guess and I'm sticking to it.
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AvatarGreg Miller
No issues on doing that on exam for actual "points".. just wanted to see if you could get in the ballpark for a homework assignment
8:07
The "initial guess" thing was just a homework idea.. .I just wanted to see if you could use the handout with the plots to make an educated guess.
Kasey
8:06
I finished the Roadside assistance Case and I was a little unsure about the question about how accurate my initial guess was after making the 5 column chart.
AvatarGreg Miller
8:06
So, why is it called "legal" pad? Do you know?  I don't know the history on that?
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