Radium in soil. Radium-226 is a is a naturally occurring radioactive gas. Elevat

Question

Radium in soil. Radium-226 is a is a naturally occurring radioactive gas. Elevated levels of radium-226 in metropolitan Dade County (Florida), were recently investigated (Florida Scientist, Summer/Autumn 1991). The data in the table are radium-226 levels (measured in pCi/L) for 26 soil specimens collected in southern Dade County. The Environmental Protection Agency (EPA) has set maximum exposure levels of radium-226 at 4.0 pCi/L. Determine whether the mean radium-226 level of soil specimens collected in southern Dade County is less than the EPA limit of 4.0 pCi/L. Use alpha = .10.

Explanation / Answer

1)      State the appropriate null and alternative hypotheses:-

H0: >= 4      H1: < 4

2)      Specify the desired level of significance and the sample size:-

a = 0.10 and sample size is 26

3)      Determine the appropriate technique:-

is unknown and hence it is t-test

4)      Determine the critical values:-

With 25 DF and a = 0.10, we get critical value to be -1.31634507

5)      Collect the data and compute the test statistic:-

               tSTAT=x-/S/sqrt(n)

                      =2.41-4/2.08/sqrt(26)

                      =-0.1/0.24/4.36

                      =-3.9

6)      State the conclusion and interpret the result:-

Since -3.9<-1.316 and hence it falls within the rejection region, so reject H0

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