Practice Test Solutions

This is not going to work too well as I have to type them....
#11.) a.) Because n is large (over 30), skew should not be a problem. CLT is in effect here.
b.) t df=49 (235700, 3606.2)
c.) No, not unusally high as $235,700 is in the inteval
d.) keep t* = 1.676, solve for n...get n=457
#12.) t is questionable here because M2 is not normalish....anyway if we continue: a p-value of .0041 is strong evidence against the two data sets being equal. It appears the adjustments have improved the gas mileage.
#13.) a: 1 z -
b: 3 t 23
c: 2 z -
d. 5 t 14
e. 5 t 9
f. 4 t 19 (or 33.1 from technology)
#14.) a. Ho: u = 10
Ha: u > 10
b. I thought type II as this would mean that we are missing a chance to become more effecient.
c. To increase the power we can increase alpha or increase n. If we increase alpha, we run a higher risk of a tpye I error. If we increse n, it is more expensive and takes more time.
#15.) West data is skewed...we should not do a t-test. The other conditions and assumptions are OK I believe.