Answer:
11.5
The sample standard deviation measures the spread of a data distribution of the sample. It is usually used to estimate the population standard deviation
The first option and the third option are correct.
(Although, it's probably way too late now...)
Answer:
Step-by-step explanation:
Given that a researcher is trying to decide how many people to survey.
We have confidence intervals are intervals with middle value as the mean and on either side margin of error.
Confidence interval = Mean ± Margin of error
Thus confidence interval width depends on margin of error.
Margin of error = 
Thus for the same confidence level and std deviation we find margin of error is inversely proportional to square root of sample size.
Hence for small n we get wide intervals.
So if sample size = 300, the researcher will get wider confidence interval