Question

A poll of 1,000 randomly selected registered voters was taken and 680 responded that they favor candidate X for mayor (p 1 = 0.6800). Just before the election, another poll of 900 registered voters was taken and 598 individuals responded that they favor candidate X (p 2 = 0.6644). A 90% two-proportion z confidence interval for the true difference between p 1 and p 2was found to be (-0.0199, 0.0510). What is the meaning of the interval in the context of the problem? QUIZLET

Answer 1

Answer:

The interval (-0.0199, 0.0510) represents the region of values where the true difference (in population terms now) between the initial proportion of registered voters that favour candidate X and the proportion of registered voters that favour candidate X just before election can take on with a confidence level of 90%.

Step-by-step explanation:

Confidence Interval for the population proportion is basically an interval of range of values where the true population proportion can be found with a certain level of confidence. It is usually obtained from the sample.

p₁ represents the proportion of registered voters that favour candidate X in the initial poll, way before the election.

p₂ represents the proportion of registered voters that favour candidate X in the poll just before the election.

So, for this question the confidence interval for the true difference between the population proportion of registered voters that favour candidate X way before the elections and the population proportion that favour candidate X just before the election lies within (-0.0199, 0.0510) with a confidence interval of 90%.

Confidence interval is calculated mathematically as thus:

Confidence Interval = (Difference in Sample proportion) ± (Margin of error)

Margin of Error is the width of the confidence interval about the difference in the two sample proportions.

It is given mathematically as,

Margin of Error = (Critical value) × (standard Error)

Critical value = 1.645 (obtained from the z-tables because the sample size is large enough to ignore that information about the population standard deviation isn't given and t-critical value approximates z-critical value)

Hope this Helps!!!