91Ó°ÊÓ

$\stackrel{¯}{x}=50,n=16,\mathrm{σ}=5$

The formula used:$\stackrel{¯}{x}-\frac{2\mathrm{σ}}{\sqrt{n}}\text{to}\stackrel{¯}{x}+\frac{2\mathrm{σ}}{\sqrt{n}}$

Find a $95\%$confidence interval for the population mean.

Consider $\stackrel{¯}{x}=50,n=16$, and $\mathrm{σ}=5$

Empirical rule:

Property 1: Around $68\%$of the data set is located between $(\stackrel{¯}{x}-s,\stackrel{¯}{x}+s)$

Property 2: Approximately $95\%$of the data set is contained within the range $(\stackrel{¯}{x}-2s,\stackrel{¯}{x}+2s)$

Property $3: Approximately $99.7\%$of the data set is located between $(\stackrel{¯}{x}-3s,\stackrel{¯}{x}+3s)$

Using Property $2$, $95\%$of all observations fall within two standard deviations of the mean on either side.

The $95\%$confidence interval for the population mean is,

Thus, the $95\%$ confidence interval for the population mean is from $47.5$ to $52.5$

Identify the margin of error.

From part a., the margin of error is $\mathbf{2}\mathbf{.}\mathbf{5}$

Interpretation:

With $95\%$ confidence, the population mean $\left(\mathrm{μ}\right)$ can be projected to be within $2.5$ of our sample mean.

In terms of the point estimate and the margin of error, express the confidence interval's endpoints.

The point estimate and margin of error endpoints of the confidence interval are as follows: Point estimate $Â\pm$ Margin of error $=50Â\pm 2.5$