1. Tiffany's class did an experiment to prepare a compound by reacting copper and sulfur. The following is the account of Tiffany's experiment. I weighed some coppet powder and added excess sulfur powder to it. After mixing, a yellow-brown mixture was formed. I heated the mixture in a test tube. It glowed red-hot. A blue-grey solid was formed. I removed the excess sulfur with xylene and obtained the blue-grey solid left behind. (a) Tiffany has left out the details of how she removed the excess sulfur. Describe the procedure she should have used. (Hint: Only sulfur is soluble in xylene.)

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.

i'm wiling to try and you : )

може ли да зареждате повече информация, моля

more infor would

a lot