Suppose we conduct a poll to estimate the proportion of...

Suppose we conduct a poll to estimate the proportion of voters who favor a major presidential candidate. Assuming that 50 percent of the electorate could be in favor of the candidate, determine the sample size needed so that we are 95 percent confident that pˆ , the sample proportion of voters who favor the candidate, is within a margin of error of .01 of p, the population proportion of all voters who are in favor of the candidate. n = ____ voters

Transcript

00:02 Hello there.

00:04 For this question, i see that they want us to assume that 50%, let's write that down, 50%.

00:14 I'm right down assume, so we just go along with it.

00:22 They want us to assume.

00:27 Sorry, i'm just putting it down, to make it look better, assume that 50 % that 50 % of the electorate.

00:36 The electorate could be in favor of a candidate.

00:43 They wanted to determine the sample size needed.

00:47 So 95 % confident that p, p, the sample portion, is within the margin of error.

01:14 Of 0 .1 of p the population put so they want us to find the population portion of all the photos who are in favor of this candidate so how we're going to go about that so let me write down 0 .1 that's our margin of error okay so they told us those things so how are going to go about determining the sample size, well, to determine the sample side that you would need, you know down sample size, you would need your c score to the power two times your standard deviation times one minus.

02:28 Okay, i don't get rid of it, okay.

02:31 One minus your standard deviation.

02:38 Oh, oops, over your confidence in a confidence interval.

02:54 This is by the power of two.

02:55 So that's what we're supposed to do.

02:59 So, oops.

03:01 So we see we got 95 % as our confidence, because so we got that.

03:11 So what we have left is that we have to find our c score and our standard deviation.

03:17 So how will we go about? this okay never mind i mess up we got to go by our zero point one as our confidence interval and we need the 95 % for our c score my bad so what will be our standard deviation our standard deviation would be 50 % or we just say 0 .5 okay so now we got all that down let's try to do the first step, oops, is to find our c score.

03:56 So we know that 95 % is the confidence.

04:01 So go find your sc score chart and find out where our 95 % would be.

04:15 So our c score for 95 % would be, let me write on the bottom.

04:26 Okay, oops, sorry.

04:29 So our c score for 95 % would be 1 .96.

04:41 And they have a setup where you might not, it's hard if you to find it, but they'll place it on the side.

04:48 That's where they'll place like 90%, 95, 98, and 99.

04:55 So you'll see a setup where 90 % is 1 .645.

05:02 95 is basically 1 .96...