What is the ratio strength of 100 ml containing a 1: 50 povidone iodine solution diluted to 1000 ml? (answer must be numeric; no units or commas; do not enter the 1 and the colon; enter only the number after the colon, as shown here with xs: 1:

We are given that:

100 mL total solution with 1:50 povidone iodine solution

This means that there is 1 mL of povidone iodine solution per 50 mL of total solution. Since we are given a total of 100 mL solution, therefore we have an initial amount of:

pure povidone iodine solution = 2 mL

This amount of pure povidone iodine solution is added or diluted (most perhaps with water) to make a total of 1000 mL total solution, therefore the new ratio is:

2:1000 povidone iodine solution

By dividing both sides by 2, this simplifies to

1:500 povidone iodine solution

1:500

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.