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This is a Korean CSAT mathematics multiple-choice problem. Solve it and put only the correct choice symbol, one of ①, ②, ③, ④, ⑤, inside \boxed{}.
Problem 26 A population is normally distributed with meanmand standard deviation 5. From this population, a random sample of size 36 is taken, and a 99% confidence interval for the population meanmis constructed using the sample mean. The resulting confidence in- terval is 1.2≤m≤a. Find the value ofa. (Here,Zdenotes a standard normal random variable, and use P(|Z| ≤2.58) = 0.99.) [3 points] ①5.1 ②5.2 ③5.3 ④5.4 ⑤5.5
The standard error is .
For a 99% confidence interval, the margin of error is
So the interval width is . Given the lower bound ,
\boxed{⑤}
Comparative Analysis (P25) (Average across runs)
Averages use reported measurements only. Missing usage is not treated as zero.