Answer:
They can either decrease the confidence level or increase the sample size, that is, survey more students.
Step-by-step explanation:
The width of a confidence interval is given by:
In which z is the critical value correponding to the confidence level(higher confidence level, higher z is), 
is the standard deviation of the population and n is the size of the sample.
The students realize that this interval contains a large margin of error. What can they do to make a narrower interval?
Looking at the formula for M, they can either decrease the confidence level or increase the sample size, that is, survey more students.
Answer: 18.36
Step-by-step explanation:
Replace "z" with "2":
.
If an integer is chosen between 1 and 50 inclusive, you have 50 numbers total to deal with, so 50 is in the denominator of our ratio (fraction). All the numbers divisible by 3 in that interval total 16 numbers. So the ratio would be 16/50 for a percentage of 32%
Let's call the 10 runners A B C D E F G H I J
ABC
ABD
ABE
ABF
ABG
ABH
ABI
ABJ
ACB
ACD
ACE
ACF
ACG
ACH
ACI
ACJ
ADB
ADC
ADE
ADF
ADG
ADH
ADI
ADJ
AEB
AEC
AED
AEF
AEG
AEH
AEI
AEJ
AFB
AFC
AFD
AFE
AFG
AFH
AFI
AFJ
AGB
AGC
AGD
AGE
AGF
AGH
AGI
AGJ
AHB
AHC
AHD
AHE
AHF
AHG
AHI
AHJ
AIB
AIC
AID
AIE
AIF
AIG
AIH
AIJ
AJB
AJC
AJD
AJE
AJF
AJG
AJH
AJI
The above is 60 different ways, but now B C D E F G H I J have to come first, and the proses starts again, until we have covered them all. I'm not going to write them all out but in theory, there is 540 different ways. 9*60=540.
