Question

Twenty nine concrete blocks were sampled and tested for crushing strength in order to estimate the proportion that were sufficiently strong for a certain application. Twenty seven of the 29 blocks were sufficiently strong. Use the small-sample method to construct a 95% confidence interval for the proportion of blocks that are sufficiently strong.

Answer 1

Answer:

95% confidence interval for the proportion of blocks that are sufficiently strong

(0.83913 , 1.02293)

Step-by-step explanation:

Step:-1

Given that the sample size 'n' = 29 blocks

Estimate proportion

                       $p = \frac{x}{n} = \frac{27}{29} = 0.93103$

Step:-2

95% confidence interval for the proportion of blocks that are sufficiently strong

$(p^{-} -Z_{0.05} \sqrt{\frac{p(1-p)}{n} } , p^{-} + Z_{0.05} \sqrt{\frac{p(1-p)}{n} } )$

$(0.93103 -1.96 \sqrt{\frac{0.93103(1-0.93103)}{29} } , 0.93103 + 1.96 \sqrt{\frac{0.93103(1-0.93103)}{29} } )$

(0.93103 -  0.0919 , 0.93103 +0.0919)

(0.83913 , 1.02293)

Final answer:-

95% confidence interval for the proportion of blocks that are sufficiently strong

(0.83913 , 1.02293)