Answer:
C.
X = -5
Step-by-step explanation:
Answer:
Standard error
Step-by-step explanation:
The standard deviation of the distribution of sample means is called the standard error of the means.
It is denoted by: 
The standard error is calculated using the formula: 
where n is the sample size and
is the population standard deviation.
Answer:
18
Step-by-step explanation:
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The first box should be correct
30 + c = 40