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Two Super Quick S1 questions

2.png

Found last part to be 18.2 and then I tried to use linear interpolation but it didn't seem to work :/

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I get that Syy rises, but why doesn't Sxy rise if y rises?

(only need a hand on the last part of each question)
3.png75.2KB
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Avatar for Zacken
Zacken
22
Original post by creativebuzz
I get that Syy rises, but why doesn't Sxy rise if y rises?


Because if the change in y is negated by the change in yˉ\bar{y} and hence this means that the y−yˉy - \bar{y} term in the summation doesn't really change when summed over, and hence SxyS_{xy} doesn't change.
Original post by Zacken
Because if the change in y is negated by the change in yˉ\bar{y} .


But Syy increases so surely the change in y is not negated by the change is y bar
Original post by Zacken
Because if the change in y is negated by the change in yˉ\bar{y} and hence this means that the y−yˉy - \bar{y} term in the summation doesn't really change when summed over, and hence SxyS_{xy} doesn't change.


Sorry to be so annoying but would you mind explaining?
Reply 4
Avatar for veejn
veejn
1
Original post by creativebuzz
Sorry to be so annoying but would you mind explaining?


for the new name, x-xbar is 0, meaning Sxy doesn't change because when multiplying x-xbar by y-ybar for the new name, you get zero so the overall sum remains unchanged
Original post by veejn
for the new name, x-xbar is 0, meaning Sxy doesn't change because when multiplying x-xbar by y-ybar for the new name, you get zero so the overall sum remains unchanged


Ohhh now I understand, thanks! :smile:

Would you mind giving me a hand on the first picture I posted in the first post of this thread? (I only need help on the last part of that question) (the tomato one)

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