The $6.76 and $6.94 is the interval Julie can be 95% certain that the sample means will fall within option (A) is correct.
It is defined as the measure of data disbursement, It gives an idea about how much is the data spread out.
[tex]\rm \sigma = \sqrt{\dfrac{ \sum (x_i-X)}{n}[/tex]
σ is the standard deviation
xi is each value from the data set
X is the mean of the data set
n is the number of observations in the data set.
From the central limit theorem:
σ(x) = σ/√n
The standard deviation σ = $1.25
The sample n = 180
σ(x) = 1.25/√180
σ(x) = 1.25/√1801
σ(x) = 0.0931
The lower limit = 6.85 - 0.0931 = 6.756 = 6.76
The upper limit = 6.85 - 0.0931 = 6.943 = 6.94
Thus, the $6.76 and $6.94 is the interval Julie can be 95% certain that the sample means will fall within option (A) is correct.
Learn more about the standard deviation here:
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