A population is normally distributed with mean and standard deviation . From this population, a random sample of size is taken, and a confidence interval for the population mean is constructed using the sample mean. The resulting confidence interval is 1.2 $$\leq$$ m $$\leq$$ a. Find the value of . (Here, denotes a standard normal random variable, and use .) [3 points]Compute .\
[THOUGHT] To find the value of in the 99% confidence interval , we use the formula for the confidence interval of the population mean:
Given:
- The lower bound of the interval is .
- The population standard deviation .
- The sample size .
- The Z-score for 99% confidence is .
The margin of error (ME) is calculated as:
Since the confidence interval is symmetric around the sample mean , the sample mean is the midpoint of the interval:
The lower bound of the interval is:
Substituting :
Solving for :
Thus, . [/THOUGHT] [PYTHON]
Calculate the margin of error
Z = 2.58 sigma = 5 n = 36 ME = Z * (sigma / (n ** 0.5))
Lower bound of the interval
lower_bound = 1.2
Calculate the sample mean (midpoint)
sample_mean = lower_bound + ME
Calculate the upper bound 'a'
a = 2 * sample_mean - lower_bound
Compute 10a
result = 10 * a print(result) [/PYTHON]
[THOUGHT] The Python output confirms that , which rounds to the integer . This matches our earlier derivation. [/THOUGHT] \boxed{55}