AP Statistics 4.7.C Calculating Two-Sample t-Intervals

Practise constructing a two-sample t-interval for the difference between population means from independent sample summaries and reporting its ordered bounds.

Exam points

Calculate x-bar1 minus x-bar2 plus or minus t-star times its standard error, preserving group order and units.

[Maximum number: 1]

Cumulative exposure to nitrogen dioxide ( $\mathrm{NO}_{2}$ ) is a major risk factor for lung disease in tunnel construction workers. In one study, researchers compared cumulative exposure to $\mathrm{NO}_{2}$ (in parts per million per year, ppm/yr) for a random sample of drill and blast workers and for an independent random sample of concrete workers. Summary statistics are shown in the following table:
\begin{tabular}[t]{|l|l|l|l|}
\hline Tunnel Worker
Activity & Sample Size & Mean
Cumulative NO2
Exposure
(ppm/yr) & Standard
Deviation in
Cumulative $\mathbf{N O}_{\mathbf{2}}$
Exposure
(ppm/yr) \\
\hline Drill and
blast & 115 & 4.1 & 1.8 \\
\hline Concrete & 69 & 4.8 & 2.4 \\
\hline
\end{tabular}

Figure for Question 4.7.C—Calculate an appropriate confidence interval for the difference between two population means question 1 — AP Statistics

Assume conditions hold and use 95 percent confidence.

Calculate the confidence interval.

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4.7.C—Calculate an appropriate confidence interval for the difference between two population means question 1