Question

Using the results from a survey of 1050 elibible voters, an approximate 98% confidence interval estimate for the proportion of voters who claimed to have voted in the last presidential election was (0.61,0.678). Links to statistical tables:

NormalTable_Negz
NormalTable_Posz
Table_Df1-35
Table_D136+

Required:
What is p rounded to three decimal places?

Answer 1

Answer: p= 0.644

Explanation:

We know that, the confidence interval for population proportion is given by :-

sample proportion(p) ± Margin of error(E)

Given confidence interval : (0.61,0.678)

i.e. p- E = 0.61 ... (i)

p+E = 0.678 ...(ii)

Adding (i) and (ii), we get

2p = 1.288

p= 0.644

From (ii),

E= 0.678-0.644

E= 34

Hence, the value of p = 0.644