AQA S1 EXAM DISCUSSION THREAD of 20th May 2011

can anyone remember that we had to draw two regression lines on figure 1 and figure 2. This is how i did it.
for figure 1, y intercept, as said, was -1. so i used the regression equation
when x = 10
z (or y)= -1+(0.5*10)=4
so i drew a line from (0,-1) to (10,4). WHICH GAVE A LINE WITH A POISTIVE CORRELATION

do you think that is right?

and for figure 2 i did the same thing but obviously with different values and the line HAD A NEGATIVE CORRELATION

yeah think its right, thats what i did anyway lol. Except i put little marks for each value of x, just confirming the line really, don't know why though, the first and end are all required to get the line

I think i got most of my answers similar to Rob's. On the linear regression one, with the guy's shop i put the chance of rain on a particular day affecting the amount of money made haha, don't know if its right anyone else put that?
For the proving not mutually exclusive and not independent:
For not mutually exclusive i just wrote P(J n W) = 0.55 therefore both can happen at the same time and so are not mutually exclusive. For the not independent i said P(J n W) = 0.55 but P(J n W') and P(W n J') were different from each other and from P(J n W) (can't remember the values) and so the probability of her buying water is affected by the probability she buys juice and vice versa. Don't think it went too badly actually

I think i got most of my answers similar to Rob's. On the linear regression one, with the guy's shop i put the chance of rain on a particular day affecting the amount of money made haha, don't know if its right anyone else put that?
For the proving not mutually exclusive and not independent:
For not mutually exclusive i just wrote P(J n W) = 0.55 therefore both can happen at the same time and so are not mutually exclusive. For the not independent i said P(J n W) = 0.55 but P(J n W') and P(W n J') were different from each other and from P(J n W) (can't remember the values) and so the probability of her buying water is affected by the probability she buys juice and vice versa. Don't think it went too badly actually