Mathematics, 28.12.2019 02:31 aron7596

In exploring possible sites for a convenience store in a large neighbourhood the retail chain wants to know the proportion of ratepayers in favor of the proposal. if the estimate is required to be within 0.1 of the true proportion would a random sample of size n=100 from the council records be sufficient for a 95% confidence interval of this precision? if not, what should be the minimum sample size?

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Answer from: brittneyrenae7338

$n=\frac{0.5(1-0.5)}{(\frac{0.1}{1.96})^2}=96.04$

And rounded up we have that n=97

Based on this with a sample of 100 we have a size large enough to satisfy the condition that the margin of error would be 0.1

Step-by-step explanation:

Notation and definitions

number of ratepayers in favor of the proposal

random sample taken (variable of interest)

$\hat p$ estimated proportion of ratepayers in favor of the proposal

true population proportion of ratepayers in favor of the proposal

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

The population proportion have the following distribution

$p \sim N(p,\sqrt{\frac{p(1-p)}{n}})$

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 95% of confidence, our significance level would be given by $\alpha=1-0.95=0.05$ and $\alpha/2 =0.025$ . And the critical value would be given by: