00:01
So for this question, we need to find the minimum sample size to estimate the mean pulse rate of adult males.
00:07
And we know the confidence level, we know how strict the margin of error needs to be.
00:12
Let's work ahead a little bit.
00:14
Let's imagine we do know the sample size, n.
00:17
We go ahead and we find the sample, and we get a sample mean x bar.
00:22
So we take this and we make a confidence interval.
00:26
The formula for the confidence interval for a population.
00:31
Mean is x bar the point estimate plus and minus the margin of error z sigma over root n and we have the confidence interval we have our estimate great now i'm going to focus on this margin of error and set it to within four so less than or equal to four now if i just solve for n i'll know how big that sample had to be so that's what we're going to do but we have too many unknowns right now we need to put something in for z and something for sigma.
01:02
Z we get from the level of confidence.
01:05
So our sample here is a member of a family, every sample of size n.
01:10
And if you take the sample means, which vary a little bit, and plot them all out, you get an approximately normal distribution.
01:17
For a confidence interval, you put your point estimate in the middle, and you make an interval around it.
01:23
And say, this interval contains 98 % of the area of this curve, so we can be 98 % percent.
01:29
Confident we have captured the population mean.
01:33
That leaves 2 % in the tables.
01:36
So each tail is 1%.
01:38
0 .01.
01:39
Z is the z score to exclude these tails.
01:44
Sometimes they give you a table of confidence, levels and critical values.
01:48
But if not, you can get this from your calculator or software with the inverse normal function...