The city of Alameda is surveying residents to learn the proportion of smartphone users. They know that only smartphones use data. They sampled active cellphone plans from five service provider to determine the proportion that include data in the plan. Below are the results. What is the approximate confidence interval at 95% confidence level for population proportion of smartphones to cell phones? All cell phones (thousands)Smartphones (thousands)1007112090878754696765 1) The survey indicates that 85% to 93% of cell phone plans include data for a smartphone. 2) The survey shows that 88% to 93% of subscribers to a cell phone plan own a smartphone. 3) The survey shows that 86% to 92% of cell phone plans include data for a smartphone. 4) The survey shows that 91% to 94% of subscribers to a cell phone plan own a smartphone.

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The city of Alameda is surveying residents to learn the proportion of smartphone users. They know that only smartphones use data. They sampled active cellphone plans from five service provider to determine the proportion that include data in the plan. Below are the results. What is the approximate confidence interval at 95% confidence level for population proportion of smartphones to cell phones?  All cell phones (thousands)Smartphones (thousands)1007112090878754696765  1) The survey indicates that 85% to 93% of cell phone plans include data for a smartphone.  2) The survey shows that 88% to 93% of subscribers to a cell phone plan own a smartphone.  3) The survey shows that 86% to 92% of cell phone plans include data for a smartphone.  4) The survey shows that 91% to 94% of subscribers to a cell phone plan own a smartphone.

Leory2000 · Accepted Answer

Step 1  Form the provided data we have,  n=100+120+87+54+67=428   x=71+90+87+69+65=382  Thus,  p^=xn=382428=0.89  Step 2  The 95% confidence interval for population proportion of smartphone to cells phones is computed as,  Cl=p^±Zα2p^(1−p^)n  =0.89±1.960.89(1−0.89)428  =0.89±0.0296  Thus, the  95% confidence interval for population proportion of smartphone to cells phones is (0.86, 0.92)   Hence, the survey shows that 86% to 92% of cell phone plans include data for a smartphone.

The city of Alameda is surveying residents to learn the proportion of

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