histogram looks very nice and normal! (did you draw it?)
7.963 +/- (t*)(8.79/sqrt(27))
t* is for 26 df
I am 95% confident that the true mean difference between boys and
girls who have been drunk at least twice is between 4.5% and 11.4%
#10a)
1772/2000 = 88.6%
b) 250000/304266 = 82.2%
c) Type I = certify the petition when there are not enough sigs.
d) Type II = valid petition not certified.
e) Ho: p = 82.2% Ha: p > 82.2%
1772 and 228 > 10 check!
z = (.886 - .822)/0.008553
Note: use 0.822 in sd formula
z = 7.48, p-value = 0
We reject and say we found sig evidence that the % is greater than
82.%. Certify!
f) To increase power, collect even more sigs. Although it seems like
we have plenty of power.
#16
SRS
2 independent years
260, 240, 270 and 230 are all > 10
(0.54 - 0.52) +/- 1.96*sqrt( (.54*.46/500) + (.52*.48/500) )
I am 95% confident that the change in proportion of students who
choose to enroll is between -4.2% and 8.2%
16b) Since zero is in the interval, we would think that there is not
evidence of a change.
